THE  LIBRARY 

OF 

THE  UNIVERSITY 

OF  CALIFORNIA 

LOS  ANGELES 


GIFT 
of 
Wallace  G  Bnhoff 


&• 


G- 


GALVANIZING 

AND 

TINNING 

A    Practical   Treatise  on    the    Coating    of 
Metal  with  Zinc  and  Tin  by  the   Hot 
Dipping,  Electro   Galvanizing,  Sher- 
ardizing   and    Metal    Spraying 
Processes,  with    Information  on 
Design,     Installation     and 
Equipment    of    Plants. 


By  W.  T.   FLANDERS 

MALLEABLE   IRON    FITTINGS   Co. 

With  the   Assistance  of  the  following   Specialists 

JOHN   CALDER,  .  Metal  Coatings  Co.  of  America 

R.  D.  FOSTER,  .  Hanson  &  Van  Winkle  Co. 

C.  J.  KIRK,       .  .  U.  S.  Sherardizing  Co. 

A.  F.  SCHOEN,  .  New  Haven  Sherardizing  Co. 

Louis  SCHULTE,  .  Ele-Kem  Co. 

WM.  G.  STRATTON,  R.  N.  Bassett  Co. 

SAMUEL  TROOD,  .  Consulting  Engineer 


U.   P.   C.   BOOK   COMPANY,   INC. 
243   W.    39th    ST.    NEW    YORK 

Reprinted  1922 


COPYRIGHTED    1916 

BY 
DAVID    WILLIAMS    COMPANY 


COPYRIGHTED    1922- 

BY   THE 
U.    P.    C.    BOOK    COMPANY,    INC. 


Printed  in  U.   S.   A. 


Engineering 
L»itr» 

TS 


PREFACE 

THE  original  work  "Galvanizing  and  Tinning"  was  prepared 
to  meet  the  demand  for  reliable  information  on  the  meth- 
ods of  protecting  iron  and  steel  from  corrosion  which  the 
editors  of  the  Metal  Worker  and  The  Iron  Age  were  continually 
receiving.  Mr.  Flanders,  who  had  specialized  on  the  hot  dipping 
processes  of  coating  with  zinc  and  tin  for  many  years,  was  induced 
to  describe  the  proper  design  and  equipment  of  plants  and  the 
methods  he  had  found  most  satisfactory. 

Since  it  was  published,  many  improvements  have  been  made  in 
the  hot  galvanizing  and  tinning  processes.  Several  new  methods 
of  utilizing  zinc  and  tin  for  protection  against  corrosion  have  also 
been  devised  and  perfected.  Mr.  Flanders  did  not  feel  qualified 
to  treat  these  new  processes,  and,  as  a  majority  of  them  are  cov- 
ered by  patents,  it  was  difficult  to  obtain  practical  information 
regarding  their  application,  as  well  as  the  design  and  installation 
of  the  apparatus. 

Several  of  the  experts  who  had  specialized  on,  the  new  processes 
refused  to  contribute  because  they  deemed  their  methods  "trade 
secrets,"  while  others  supplied  splendid  advertising  matter  for  their 
special  process,  but  little  practical  data. 

The  treatment  of  hot  galvanizing  and  tinning  is  as  compre- 
hensive and  reliable  as  Mr.  Flanders'  practical  experience  could 
make  it.  This  covers  a  period  of  over  thirty-five  years  as  mechanic, 
builder  and  manager  of  plants.  Tie  was  ably  assisted  in  this  work 
by  Mr.  II.  A.  Smith,  who  contributed  a  large  amount  of  data  that 
is  new. 

In  revising  the  chapter  on  re-tinning,  Mr.  Flanders  received 
much  valuable  assistance  from  Mr.  W.  C.  Holland,  a  former  shop- 
mate,  and  from  Mr.  J.  B.  Smith,  mechanical  engineer,  and  Mr. 
W.  E.  Mumford,  metallurgist. 

Many  interesting  and  valuable  articles  by  other  experts,  bearing 


PREFACE 

on  protective  coating  of  zinc  and  tin,  which  have  appeared  in  vari- 
ous trade  papers,  have  been  included  and  proper  credit  given  in 
the  text. 

The  aim  of  all  who  have  assisted  in  the  preparation  of  .this  work 
has  been  to  make  it  of  the  greatest  practical  value  to  the  men 
actually  engaged  in  the  plant,  as  well  as  to  those  who  are  contem- 
plating the  installation  of  plants.  If  the  readers  of  the  book  fail 
to  find  the  information  they  desire,  the  publishers  will  be  pleased 
to  have  them  submit  the  problems  for  the  consideration  of  the 
experts  who  collaborated  in  making  it  so  nearly  complete. 

THE  EDITOR 

NEW  YORK,  May,  1922. 


TABLE  OF  CONTENTS 

CHAPTER  I      >/  PAGE 

Corrosion   and   Its   Prevention 9 

Theory  of  Corrosion — Galvanizing  Processes  Described — Zinc 
Coating  the  Best  Rust  Preventive — Hints  on  Selection  of  Em- 
ployees and  Handling  of  Work  and  Equipment. 

CHAPTER  II    S 

Hot  Galvanizing  Plant  and  Equipment 14 

Arrangement,  Drainage  and  Ventilation  of  the  Galvanizing  Room 
— The  Equipment — Laws  of  Physics  Applying  to  Hot  Galvan- 
izing— The  Selection  of  Proper  Grades  of  "iron  and  Steel  for  a 
Kettle— Methods  of  Testing  Material  for  Manufacture  of  Ket- 
tle— Sizes  of  Kettles  for  Different  Work — Plans  and  Details  of 
Construction  for  Different  Style  Kettles — Plan  and  Details  of 
Construction  of  Arrangement  for  Drying  Castings — Bricking  In 
a  Galvanizing  Kettle — Tanks  for  Acid  Solutions  and  Water — 
Tools  for  Galvanizing. 

CHAPTER  III  < 
The   Pyrometer 34 

Use  of  Pyrometer — Protecting  Pyrometer  from  Action  of  Zinc — 
Proper  Location  of  Pyrometer  in  Kettle — Temperature  of  Zinc 
Required  to  Secure  Uniform  Coatings — Selection  of  Pyrometer — 
Temperature  Table  and  Method  of  Calculating  Numbers  of  De- 
grees Drop  Per  Hour  in  Molten  Zinc  While  Cooling — Correct 
Method  of  Using  Thermometer. 

CHAPTER  IV  " 
Materials   Used   in   Galvanizing 41 

Spelter — Lead — White  and  Gray  Granulated  Sal  Ammoniac — 
Zinc  Ammonium  Chloride— Muriatic,  Sulphuric  and  Hydro- 
fluoric Acids — Coke — Oil — Glycerine — Aluminum. 

CHAPTER  V    v 
Pickling          44 

Securing  Uniform  Action  Avith  Acids — Mechanical  Pickling — 
Pickling  Sheets — Over  Pickling — Under  Pickling — Acid  Con- 
sumption in  Pickling — Removing  Scale  with  Sulphuric  Acid — 
Time  Required  for  Removal  of  Scale — Removing  Scale  with 
Muriatic  Acid — Substitutes  for  Acids — Cleaning  Sandy  Castings 
with  Sulphuric  Acid — Cleaning  Castings  with  the  Aid  of  Hydro- 
fluoric Acid — Temperature  of  Pickle — A  '"Quick"  Pickle. 

CHAPTER  VI  / 

Water  Rolling,  Tumbling  and  Sand  Blasting  ...  51 
Watet  Rolling — Dry  Tumbling — Design  and  Constmction  of 
Wet  Tumbling  Barrel — Preparing  Castings  for  Tumbling — Load- 
ing Tumbling  Barrel — Time  Required  to  Clean  Work  in  Ti'm- 
bling  Barrel — Mixtures  for  Cleaning  Castings  in  Tumbling  Bar- 
rel—Testing Castings  to  See  if  They  are  Properly  Cleaned — 
Re-charging  Tumbling  Barrel — Handling  Delicate  Castings  in 
Tumbling  Barrel — Storing  Castings  After  Tumbling — Prepairing 
3 


J 


4  CONTENTS 

PAGE 

Work  for  Galvanizing  or  Tinning  With  the  Sand  Blast — Simple 
Home-made  Type — Single  Hose  Type  Apparatus — Two  Hose  Type 
Apparatus — Sand  Blast  Rolling  Barrel — Air  Pressures  Re- 
quired in  Sand  Blasting — Construction  and  Ventilation  of  Sand 
Blasting  Room — Condition  of  Sand — Diamond  Grit  and  Steel 
Shot  Used  as  Substitute  for  Sand— Preparing  the  Cleaned  Work 
for  the  Dipping — Drying  the  Work. 

CHAPTER  VII  ^ 

Hot  Process  of  Galvanizing 66 

Filling  a  New  Kettle — Firing  a  New  Kettle — The  Temperature 
of  the  Zinc — Dipping  the  Work  in  the  Molten  Zinc — Removal 
of  Surplus  Zinc — Drying  and  Cooling  Work — Cost  of  Production. 

CHAPTER  VIII  >/ 
Galvanizing  Sheets 73 

Galvanizing  Sheets  by  Hand — Construction  of  Davies  Machine 
for  Galvanizing  Sheets — Davies  Method — Heathfield  Method — 
Bayliss  Process — Material  Required  to  Galvanize  Sheets. 

CHAPTER  IX    \/ 
Galvanizing  Wire,  Netting  and  Tubes 77 

An  Improvement  in  Galvanizing  Wire  Cloth — The  Influence  of 
Galvanizing  on  the  Strength  of  Wire — Tests  Used  to  Determine 
Strength  of  Wire — Absorbed  Hydrogen  Gas  Does  Damage — The 
Automatic  Galvanizing  of  Tubes — Plan  and  Elevation  of  Ma- 
chine for  Automatic  Galvanizing  of  Tubes. 

CHAPTER  X    * 

By-Products  of  the  Hot  Galvanizing  Process      ...       84 

Zinc  Dross — Running  Over  or  "Sweating"  Zinc  Dross — Plan  and 
Details  of  Construction  for  Kettle  Used  in  Recovering  Zinc 
Dross — Sal  Ammoniac  Skimmings — Screening,  Storage  and  Re- 
covery of  Zinc  Ashes. 

CHAPTER  XI  «/ 
Replacing  Old  Galvanizing  Kettles 92 

Life  of  Kettles — Repairing  Leaks  in  Kettles — Tools  for  Boiling 
Out  Kettles. 

CHAPTER  XII  • 

The  Schoop  Metal  Spray  Process 94 

Evolution  of  Apparatus — Operation  of  Old  Stationary  Type — 
Details  of  Construction  of  Old  Stationary  Type — Operation  of 
First  Portable  Type — Details  of  First  Portable  Type — Opera- 
tion of  the  Cyclone  Apparatus — Details  of  Construction  and 
Operation  of  Modern  Spraying  Pistol — Melting  Point  of  Zinc  and 
Tin  in  Schoop  Process — Gas  Pressure  Required — Applying  the 
Coating — Thickness  of  Deposit — Cost  of  Coating. 

CHAPTER  XIII 

Tinning  Malleable   Iron  Castings,  Wrought  Iron,  and 

Steel         106 

Plant  and  Equipment — Plan  of  a  Tinning  Plant — Tools  and 
Kettles. 


a. 

CONTENTS  5 

PAGE 

CHAPTER  XIV 

Preparing  the  Work  for  Tinning     \s Ill 

Removing  Scale  and  Rust  with  Sulphuric  Acid — Cleaning  Sandy 
Castings  with  Sulphuric  Acid — Cleaning  with  Muriatic  Acid — 
Cleaning  Sandy  Castings  with  Hydrofluoric  Acid — Water  Rolling 
— Removing  Paint  or  Grease. 

CHAPTER  XV  S 

Applying  the  Coating  of  Tin 115 

Tinning  with  Two  or  More  Kettles  of  Tin — Setting  Up  the 
Kettles — Passing  the  Work  Through  the  Tinning  Kettle — Tem- 
perature and  Time  Required — Tinning  Wire  in  Coils — Tinning 
Steel  Spoons  and  Similar  Articles. 

CHAPTER  XVI    \/ 

Re-Tinning 121 

Construction  of  Re-tinning  Plan  Having  Four  Kettles — Tools 
Required — Method  of  Handling  Work — Use  of  Listing  Kettle — 
Removal  of  Surplus  Tin  in  Skimming  Kettle — Finishing  of  Re- 
tinned  Work — Replacing  Re-tinning  Kettles. 

CHAPTER  XVII  S 

Tinning  Gray  Iron  Castings 129 

Plans  of  Plants,  Showing  Arrangement  of  Equipment — Eleva- 
tions and  Details  of  Construction  of  Kettles — Tools  Required. 

CHAPTER  XVIII    \S 

Preparing  Gray  Iron  Castings  for  Tinning     ....     133 

Removing  Sand  from  the  Castings — Freeing  Gray  Iron  Castings 
from  Sand  by  Hydrofluoric  Acid — Cleaning  Sandy  Castings  with 
Sulphuric  Acid — Cleaning  Castings  with  the  Sand  Blast — The 
Use  of  Hot  Alkali  Bath  in  Certain  Cases — Tumbling — Water 
Rolling. 

CHAPTER  XIX     *^ 

Coating  Gray  Iron  Castings  with  Tin 138 

Dipping  the  Castings — Flux  for  Tinning  Kettle — Handling  Cast- 
ings in  Roughing  Kettle — Time  Required  to  Tin  Castings — Re- 
moval of  Slag  from  Kettle — Proper  Heat  for  Tinning — Construc- 
tion of  Oil  Tank — Tongs  Used  in  Tinning — Construction  and  Use 
of  Switching  Box — Tinning  with  Three  Kettles  of  Tin — Effect 
of  Overheating — Storage  of  Dross. 


CHAPTER  XX 

Cleaning  Old  Galvanized  and  Tinned  Work  ....      146 

Cleaning  Old  Galvanized  Work — Refinishing  Old  Galvanized 
Work— Cleaning  Old  Tinned  Work — Kettles  for  Refinishing  Old 
Galvanized  and  Tinned  Work. 


6  .          CONTENTS 

CHAPTER  XXI 

Electro-Galvanizing   Plant  and  Equipment  ^  148 

Electro-Galvanizing — Equipment  for  Electro-Galvanizing  Plant 
— Mechanical  Galvanizing  and  Patented  Devices — The  Miller 
Chain  Conveyer  Machine — Daniels  Screw  Conveyer  Machine^- 
The  Fleischer  Cable  or  Chain  Conveyer  Machine — The  Daniels 
Barrel — The  Pothoff — The  Schulte  Barrel — The  Ele-Kem  Galvan- 
izing Barrel — A  Cleaning.  Rinsing  and  Plating  Barrel  Unit — 
Modified  Form  of  the  Cleaning,  Rinsing  and  Plating  Barrel  Unit 
— The  Meaker  Continuous  Type  Machine — Hanson  &  Van  Winkle 
Pipe  and  Tube  Galvanizing  Machine— The  Pothoff  Tube  Galvan- 
izing Machine— King's  Continuous  Wire  Cloth  Machine— The 
Root  Wire  Cloth  Machine — Schulte  Wire  Galvanizing  Machine — 
Electrical  Equipment — Anodes — Cost  of  Installation. 

CHAPTER  XXII   S 

Preparing  Work  for  Electro-Galvanizing 209 

Removing  Sand  from  Castings — Removing  Oil  or  Grease — Re- 
moving Mill  Scale — Scratch-Brushing — Copper  Flashing — Tum- 
bling and  Sand  Blasting — Schulte  Grinding  and  Scouring  Ma- 
chine— Electro-Cleaning. 

CHAPTER  XXIII  ^ 

Electro-Galvanizing  Solutions  and  Their  Application     .     217 
Composition   of   Galvanizing   Solutions — Twenty-four   Good   For- 
mulas— Agents  for  Experimenting  on  or  Improving  Solutions — 
Modern  Methods  of  Applying  the  Coatings — Cost  of  Operation — 
Tests  for  Thickness  of  Zinc  Coating. 

CHAPTER  XXIV  ^ 

The  Art  of  Sherardizing 227 

Dry  Galvanizing  in  Prehistoric  Times — Theory  of  Sherardizing 
— How  Precipitation  of  a  Vapor  on  Metal  Occurs — Methods  of 
Producing  Zinc  Vapor. 

CHAPTER  XXV  v/ 

Location  and  Equipment  of  the  Sherardizing  Plant  .      .     233 
Cleaning  Apparatus — The  Sherardizing   Furnace  or  Oven — Coke 
Burning    Furnaces — Gas    and    Oil    Burning    Furnaces — Electric 
Heated    Furnaces — Wiring   Diagrams — Drums — Dust    Separating 
Machine —  The  Transfer  Car — Cooling  Frames — Pyrometers. 

CHAPTER  XXVI  " 

Materials  Used  in  Sherardizing 256 

Dust  from  the  Zinc  Smelter — Freeing  Dust  from  Iron — Use  of 
Manufactured  Zinc  Dust — Method  No.  1  for  Determining  Metal- 
lic Zinc  in  Zinc  Dust — Method  No.  2  for  Determining  Metallic 
Zinc  in  Zinc  Dust — Method  No.  3  for  Determining  Metallic  Zinc 
in  Zinc  Dust.  / 

CHAPTER  XXVir 

Preparing  Material  and  Loading 261 

Pickling  of  Steel — Pickling  Malleable  and  Gray  Iron  Castings 
— Loading  the  Drums — Packing  the  Electric-Heated  Drum. 


CONTENTS  7 

CHAPTER  XXVIII  PAGE 

Temperature  and  Duration  of  Heats    .   ^   ....     267 

Thickness  of  Coating — Temperature  an  Important  Factor — 
Operation  of  the  Electric-Heated  Drum — Shorardizing  with  Zinc 
Under  Vacuum — Time  an  Important  Factor — Motion  During 
Sherardizing — General  Operation — Cooling  and  Unloading. 

CHAPTER  XXIX    / 

Don'ts  in  Sherardizing  Practice 278 

Eliminating  Black  Spots  on  Finished  Work — Obviating  Non- 
Uniformity  of  Coating — Improving  Psychological  Condition  of 
Men — Caution — Don'ts. 

CHAPTER  XXX     S 
Coloring  and  Finishing  Sherardized  Articles  ....     282 

Buffing — Cutting  Do\vn — Burnishing — Nickel — Copper — Bronze — 
Japanning — Enameling — Lacquering. 

CHAPTER  XXXI   / 

Cost  of  Sherardizing  Material  Per  Ton  with  Different 

Fuels 287 

Cost  for  Fuel  Oil  Burning — Producer  Gas — Coke — Illuminating 
Gas — Disposal  of  Used  Zinc  or  Zinc  Residue. 

CHAPTER  XXXII  ^ 

Galvanizing  Specifications  and  Tests 291 

Specifications  for  Hot  and  Electro-Galvanizing — Preece  or  Copper 
Sulphate  Test — Limitations  of  the  Preece  Test — Lead  Acetate 
Test — Caustic  Soda  Test — The  Preece  Test — Manipulation  and 
Temperature  of  the  Preece  Test — Consideration  of  Objections  to 
Preece  Test — Manipulation  of  Lead  Acetate  Test — Preece  and 
Lead  Acetate  Tests  Compared — Electrolytic  Methods  of  Testing 
— Caustic  Soda  Test — Government  Test — Salt  Spray  Test — Con- 
struction of  Box  for  Salt  Spray  Test — Chart  of  Comparative 
Tests — Hydrochloric  Acid  and  Antimony  Chloride  Tests  for 
Sheets  and  Wire. 


Galvanizing  and  Tinning 


CHAPTER  I 

Corrosion  and  Its  Prevention 

IRON  and  steel  will  invariably  rust  or  corrode  if  exposed  to 
the  atmosphere  without  protection,  and  Mr.  Alfred  Sang,  in 
The  Iron  Age,  explains  the  reasons  for  this  fact  in  an  ex- 
cellent manner,  as  follows: 

"One  of  the  most  persistent  problems  which  confront  the 
worker  in  iron  and  steel  is  the  prevention  of  corrosion.  "We  can- 
not rid  ourselves  of  the  agents  which  effect  the  corrosion  of  iron 
without  at  the  same  time  ridding  ourselves  of  the  agents  which 
are  essential  to  life  itself. 

"Air  is  indispensable  both  to  human  respiration  and  for  the  for- 
mation of  rust  and  other  oxides,  for  which  it  supplies  the  oxy- 
gen; moisture  is  necessary  for  the  formation  of  clouds,  which 
make  the  earth  fertile,  and  it  also  supplies  the  medium  in  which 
rusting  takes  place  and  hydrates  the  oxide;  carbonic  dioxide  is 
an  animal  by-product  and  a  raw  material  for  the  vegetable  world, 
and  the  exchange  of  carbonic  dioxide  and  oxygen,  which  is  con- 
tinually taking  place  between  the  animal  and  the  vegetable  king- 
dom, is  of  vital  importance.  Then,  on  the  other  hand,  rust  is  not 
readily  formed,  if  at  all,  unless  there  be  an  acid  present,  and  the 
acid  which  is  most  universally  distributed  is  carbonic  acid,  or 
hydrated  carbonic  dioxide. 

"There  is,  as  you  see,  a  close  relationship  between  the  processes 
of  living  and  rusting,  but,  while  human  beings  make  up  for  the 
rusting  or  decaying  of  their  tissues  by  nutrition,  it  has  not  yet 
been  discovered  how  to  feed  or  regenerate  iron,  and  until  such 
a  discovery  is  made  we  are  compelled  to  take  our  cue  from  the 
ancient  Egyptians  and  resort  to  embalming. 

"There  are  two  general  ways  of  embalming  iron  to  prevent 
its  decomposition,  which  might  be  called,  respectively,  the  metal- 
lic and  non-metallic  methods.  In  the  non-metallic  method  the  ar- 


10  GALVANIZING  AND  TINNING 

tides  are  coated  with  an  organic  substance,  usually  oil,  or  varnish, 
the  efficiency  of.  which  depends  on  its  being  more  or  less  airtight; 
when  coloring  matter  is  added  to  the  oil  it  becomes  a  paint,  but  I 
understand  from  authorities  on  the  subject  that  a  varnish  free 
from  pigments  is  preferable  to  anything  else.  The  metallic 
method  consists  of  coating  the  iron  with  some  other  metal,  and 
it  is  this  method  which  I  have  come  to  discuss  with  you. 

"Iron  rusts  less  easily  than  does  steel;  this  is  perhaps -due  to 
steel  being  a  very  composite  material.  In  the  iron,  which  forms 
the  bulk  of  its  composition,  are  dissolved  or  immersed  a  great 
variety  of  other  substances;  some  of  these  are  simple,  such  as 
graphite,  silicon  and  manganese,  and  others  are  compound,  such 
as  carbides,  sulfides,  phosphides  and  silicides.  The  carbon  com- 
pounds are  very  numerous  and  diversified,  being  due  to  different 
heat  treatments;  the  best  known  are  cementite,  pearlite  and  mar- 
tensite.  Just  as  variety  is  to  some  people  the  spice  of  living,  so  is 
heterogeneous  composition  the  spice  of  rusting,  in  the  present  in- 
stance at  any  rate.  Nor  is  this  by  any  means  a  solitary  instance : 
it  is  a  well-known  fact  that  chemically  pure  zinc  is  dissolved  very 
slowly  by  certain  acids,  whereas  the  commercial  product,  especially 
if  it  be  high  in  iron,  is  rapidly  dissolved." 

Great  trouble  and  expense  annually  falls  upon  manufacturers, 
metal  workers  and  property  owners  through  the  rusting  or  cor- 
roding of  iron  and  steel.  An  illustration  of  this  is  shown  by  the 
following,  which  recently  appeared  in  The  Iron  Age: 

"The  receivers  of  Milliken  Brothers,  Incorporated,  11  Broad- 
way, New  York,  have  lately  made  some  extensive  experiments  in 
connection  with  protecting  from  oxidation  steel  grillage  beams 
used  in  building  construction.  More  or  less  water  is  present  in 
nearly  every,  building  where  grillage  beams  are  used.  There- 
fore, unless  the  beams  are  absolutely  protected,  there  will  be  oxi- 
dation. As  such  beams  are  not  usually  exposed  to  view  and  can- 
not be  examined,  if  oxidation  takes  place  after  the  building  is  up 
and  the  oxidation  becomes  serious,  the  security  of  the  building  is 
threatened. 

"Finding  that  coating  the  beams  with  paint,  asphalt  or  tar 
cannot  be  absolutely  relied  on  for  a  great  length  of  time,  Milli- 
ken Brothers  have  experimented  with  galvanizing  by  the  hot 
process,  after  all  the  shop  work  has  been  done  on  the  steel.  It 
has  been  shown  that  concrete  will  adhere  to  galvanized  steel 


CORROSION  AND  ITS  PREVENTION  11 

beams  as  firmly  as  to  unpainted  beams,  and  much  better  than  to 
painted  beams.  Architects  and  engineers  who  have  had  occasion 
to  examine  galvanized  Ashlar  anchors  and  galvanized  pipes  used 
in  connection  with  concrete  have  found  that  concrete  will  attach 
itself  as  readily  to  galvanized  material  as  ungalvanized  material. 
The  advantage  of  galvanizing  is  that  it  gives  the  steel  beam  a 
complete  zinc  coating  which  will  resist  the  action  of  the  water  and 
therefore  protect  the  steel.  The  expense  connected  with  the  gal- 
vanizing is  considered  small  in  comparison  with  the  resulting 
benefits." 

Zinc  Coating  the  Best  Rust  Preventive 

It  is  my  purpose  in  this  volume  to  deal  with  the  subject  of  coat- 
ing iron  and  steel  products  with  zinc,  or,  as  generally  termed,  gal- 
vanizing them  (to  prevent  rusting),  which  has  become  a  large  and 
important  industry  in  which  much  capital  is  invested  and  many 
men  are  employed.  Zinc  is  without  doubt  the  best  protective  coat- 
ing for  iron  and  steel,  and  the  reasons  are  clearly  stated  in  The 
Brass  World,  which  says: 

"It  is  difficult  for  many  persons  to  understand  why  zinc  is  the 
best  rust  preventive  for  iron  or  steel,  and  they  believe  it  is  on  ac- 
count of  its  cheapness  that  it  is  so  extensively  used.  They  have  an 
idea  that  lead,  being  a  cheaper  metal,  would  answer  far  better,  and 
as  it  is  more  non-corrosive  than  zinc,  would  protect  the  iron  better. 
This  is  not  a  fact,  however,  as  will  subsequently  be  explained. 

"The  very  fact  that  zinc  is  a  corrosive  metal  does  not  affect  its 
properties  when  applied  as  a  coating  to  iron  or  steel.  Indeed,  if  it 
did  not  corrode,  it  would  not  be  of  value  for  such  a  purpose.  When 
iron  or  steel,  which  has  been  coated  with  zinc,  is  exposed  to  the 
atmosphere,  a  galvanic  action  is  set  up,  although,  of  course,  ex- 
tremely slight.  Any  two  dissimilar  metals  form  a  galvanic  couple, 
but  as  zinc  is  the  most  electropositive  metal,  the  galvanic  action 
between  the  zinc  and  iron  is  as  great  as  could  be  obtained  when 
iron  is  used  for  one  of  the  metals  composing  the  couple. 

"The  result  is,  therefore,  that  with  the  slight  galvanic  action  set 
up  on  galvanized  iron  or  steel,  when  exposed  to  the  atmosphere,  a 
corrosion  takes  place.  Did  it  not  follow,  then  there  would  be  no 
protection.  In  this  case,  the  zinc,  being  the  electropositive  metal, 
suffers  corrosion  at  the  expense  of  the  electro-negative  metal  iron. 
The  effect  is  that  the  corrosion  goes  on  with  the  zinc  exclusively 


12  GALVANIZING  AND  TINNING 

and  iron  is  not  corroded  at  all,  provided  any  zinc  is  left  on  the 
iron  or  steel.  This  condition  takes  place  whether  a  light  or  heavy 
coating  of  zinc  is  present.  The  only  advantage  of  a  heavy  zinc 
coating  is  that  it  will  last  longer,  but  under  ordinary  atmospheric 
conditions,  where  a  slight  amount  of  moisture  is  the  only  exciting 
liquid,  the  galvanic  action  is  very  small  and  the  zinc  coating,  be  it 
ever  so  light,  lasts  a  long  time.  In  the  case  of  sea-water  or  air 
saturated  with  salt  moisture,  the  corrosion,  of  course,  is  much  more 
rapid  and  a  heavier  zinc  coating  is  required  to  resist  it  for  a  length 
of  time. 

"The  reason  for  the  protection  of  iron  or  steel  by  a  zinc  coating 
is,  therefore,  on  account  of  the  fact  that  the  zinc  corrodes  at  the 
expense  of  the  iron  or  steel  by  the  galvanic  action  set  up.  Zinc, 
however,  when  exposed  to  the  air,  does  not  corrode  rapidly  or 
deeplv  and,  in  fact,  very  lightly.  This  property  is  of  great  value, 
as  the  zinc  coating  does  not  corrode  rapidly,  even  with  the  galvanic 
action  set  up,  so  that  it  lasts  for  a  far  greater  length  of  time  than 
would  naturally  be  expected.  The  very  fact,  however,  that  the  zinc 
corrodes  at  the  expense  of  the  iron  is  all  that  is  necessary  to  pro- 
tect the  iron  or  steel,  even  though  it  be  extremely, slight. 

"Other  metals  like  lead  or  tin,  on  account  of  their  not  being 
electropositive  to  iron,  do  not  act  like  zinc.  They  act  simply  as  a 
covering  like  a  paint  or  varnish,  and  if  portions  of  the  iron  happen 
to  be  exposed,  even  such  as  a  pinhole,  the  iron  begins  to  corrode. 
With  a  zinc  coating,  however,  this  will  not  take  place." 

Therefore  there  are  well  founded  reasons  for  the  growth  and 
development  of  the  galvanizing  industry,  since  zinc  is  the  best  pro- 
tective coating  for  iron  and  steel  and  is  comparatively  low  in 
price. 

The  oldest  galvanizing  process  and  the  one  most  generally  used 
is  the  hot  or  dipping  process,  although  the  "cold"  or  Electro  process 
is  used  to  considerable  extent  and  it  has  unquestionably  gained 
ground  since  its  invention,  about  twenty  years  ago.  Sherardizing 
has  come  into  use  since  the  introduction  of  the  Electro  process. 
While  its  inventor  does  not  use  the  term  "galvanizing"  in  connec- 
tion with  the  Sherardizing  process,  it  is,  in  fact,  as  truly  a  gal- 
vanizing process  as  is  the  hot  dipping  or  Electro  process.  The 
protective  coating  in  the  Sherardizing  process  is  metallic  zinc  de- 
posited from  zinc  dust  or  zinc  oxide,  while  in  the  hot  and  Electro 
processes  the  zinc  is  used  in  the  form  of  slabs  or  cast  anodes. 


G.  Imhoff 

'S~ 

CORR0SIOX  AND  ITS  PREVENTION  13 

As  the  hot  or  dipping  process  is  the  oldest,  we  will  give  it  our 
first  attention,  andl  writer  will  describe  to  the  best  of  his  ability 
methods  employed  in  the  different  branches  of  the  business,  giving 
principal  attention  to  miscellaneous  work,  such  as  gray  or  malle- 
able iron  castings,  wrought  iron  and  steel  forgings,  coal  hods,  and 
other  articles  made  from  sheet  iron,  devoting  for  obvious  reasons 
short  paragraphs  to  the  galvanizing  of  sheets,  pipe,  wire,  wire 
cloth  and  poultry  netting.  The  galvanizing  of  these  materials  is 
simply  one  process  in  their  manufacture ;  and  most  of  the  concerns 
producing  them  either  use  methods  of  their  own  or  patented  de- 
vices, which  it  would  be  unfair  on  one  hand,  and  useless  on  the 
other,  to  describe.  Job  shops  for  the  handling  of  miscellaneous 
galvanizing  are  found  in  nearly  all  large  cities  in  this  country,  and 
many  manufacturers  of  specialties  operate  their  own  galvanizing 
plants. 

It  may  not  be  out  of  place  to  say  that  it  has  been,  and  still  is, 
the  practice  of  some  engaged  in  this  business  to  make  as  much  of 
a  mystery  of  the  operations  as  possible.  Mystery  and  secret  for- 
mulae were  looked  upon  (not  so  many  years  ago  either)  as  the  key 
to  monopolizing  many  so-called  metallurgical  processes;  but  those 
times  have  passed,  and  the  reading  public  will  have  little  trouble 
in  following  out  any  present  methods  if  it  will  note  the  publica- 
tions and  lucidly  written  books  bearing  on  the  subjects  in  ques- 
tion. One  fallacy  generally  credited  is  that  galvanizing  kettles 
must  never  be  allowed  to  cool  off.  While  it  is  true  that  it  is  not 
advisable  to  allow  a  kettle  holding  several  tons  of  zinc  to  cool  off 
at  frequent  intervals,  and  it  is  not  in  the  interest  of  economy  for 
one  having  a  small  amount  of  galvanizing  to  attempt  to  do  it  him- 
self, there  is  no  reason  why  a  kettle  containing  a  few  hundred 
pounds  of  metal  cannot  be  operated  fairly  successfully,  and  pos- 
sibly to  good  advantage,  if  one  is  not  conveniently  located  for 
sending  the  work  to  a  jobbing  galvanizer.  We  wish  to  impress  the 
reader  with  the  fact  that  we  are  not  advocating  the  installation 
of  a  galvanizing  plant  as  a  matter  of  economy  unless  one  has 
sufficient  work  to  keep  it  in  constant  operation  and  employ  skilled 
help.  Unskilled  workmen  cannot  produce  best  results,  and  the 
materials  he  must  use  are  expensive.  The  operation  of  a  very 
small  plant  will  be  found  a  costly  experiment  at  the  best,  and 
should  never  be  attempted  unless  actually  necessary. 


CHAPTER  II 

Hot  Galvanizing  Plant  and  Equipment 

TO  THOSE  contemplating  the  installation  of  a  galvanizing 
plant  the  first  consideration  should  be  to  isolate  it  as  much 
as  possible  from  the  main  factory,  as  the  fumes  arising 
from  the  chemicals  used  in  the  business  are  not  only  destructive 
to  tools  and  machinery,  but  to  many  kinds  of  finished  goods.    It  is 
very  difficult  to  dispose  of  these  fumes  in  such  a  way  that  they  will 
not  prove  an  annoyance  as  well  as  a  menace  to  machinery,  tools 
and  stock. 

The  Galvanizing  Room 

In  fitting  up  a  room  or  building  in  which  to  locate  the  plant 
provision  should  be  made  to  obtain  the  best  possible  ventilation. 
The  building  should  be  high  posted,  with  a  good  ventilator  in  the 


FIG  2 — FRONT  AND  SIDE  ELEVATION  OF  A  MOVABLE  HOOD 

roof,  and  better  working  conditions  are  obtained  by  covering  the 
kettles  and  acid  tanks  with  hoods  connected  to  an  exhaust  fan  of 
suitable  size  and  speed.  If  an  exhaust  fan  is  used,  most  of  the 
fumes  arising  from  the  kettles  and  acid  tanks  can  be  discharged 
into  a  stack  or  chimney  of  suitable  height,  and  thus  disposed  of 
making  conditions  fairly  comfortable. 

14 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT 


15 


Where  hoods  are  used  over  the  kettles  and  tanks  they  should 
come  as  low  as  possible  and  not  interfere  with  the  workmen.  They 
should  be  large  enough  to  project  well  beyond  the  kettles  or  tanks 
so  as  to  catch  everything  possible  in  the  way  of  steam  and  smoke 
that  naturally  rises  when  the  plant  is  in  operation.  When  the 
work  consists  of  castings  and  other  small  articles,  there  is  no 
objection  to  having  the  hoods  come  to  within  6  feet  6  inches  of 
the  floor.  Where  hoods  are  used  on  large  kettles  they  should  be 
suspended  from  a  carriage  or  trolley  on  an  overhead  track  which 
will  permit  of  their  being  easily  moved  out  of  place  when  it  is 
desirable  to  do  so.  We  illustrate  our  method  of  putting  up  a 
movable  hood  by  Fig.  2,  although  it  is  entirely  possible  that  some- 
thing much  better  might  be  devised. 


FIG.  3 — SHOP  ARRANGEMENT  WITH  TILE  DRAINS  FOR  ACID  TANKS 

Considerable  water  is  used  in  the  hot  process  of  galvanizing 
when  miscellaneous  work  is  done,  and  provision  should  be  made 
to  secure  proper  drainage.  A  good  plan  is  to  put  catch  basins 
under  the  various  acid  and  water  tanks,  connected  by  tile  pipe  to 
sewer,  as  shown  in  floor  plan,  Fig.  3.  The  floor  can  be  cement 
or  brick. 

If  the  work  to  be  handled  is  gray  iron  it  is  not  absolutely  neces- 
sary to  use  steam,  but  if  it  is  of  a  nature  that  requires  the  re- 
moval of  scale,  or  if  malleable  castings  are  to  be  galvanized  in 
quantities,  steam  should  be  brought  into  the  room. 


16 


GALVANIZING  AND  TINNING 


A  floor  space  25  feet  by  48  feet  will  accommodate  an  outfit 
such  as  we  illustrate  in  Fig.  3.  Much  less  floor  space  can  be  made 
to  accommodate  a  very  small  plant  that  is  designed  to  operate  only 
at  irregular  intervals. 


FIG.  4 — FLOOH  PLAN  OF  GALVANIZING  ROOM  WITH  UNDERGROUND  FLUE 

Fig.  3  is  the  ground  plan  of  a  galvanizing  plant,  in  which  A  is 
a  tank  for  containing  a  solution  of  sulphuric  acid  and  water  for 
removing  scale  and  rust;  B  is  a  water  tank  for  storing  work  that 
has  been  cleaned;  C  is  a  tank  for  muriatic  acid;  D  is  a  tank  for 
hydrofluoric  acid;  E  is  the  plate  for  drying  the  work  before  im- 
mersing it  in  the  molten  zinc;  F  is  the  kettle  containing  the 
molten  zinc;  G  G  are  tanks,  one  of  which  is  divided,  and  contain 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT  17 

the  water  used  for  cooling  the  work  after  it  has  been  removed 
from  the  galvanizing  bath;  H  is  an  underground  flue  connecting 
the  drying  plate  E  with  the  chimney  or  stack  J;  K  is  a  pit  giving 
access  to  the  fire  and  ash  pit  under  the  drying  plate  E ;  M  M  are 
catch  basins,  located  under  the  several  acid  and  water  tanks,  with 
tile  pipe  connections  N  to  sewer. 

Another  plan  of  a  galvanizing  plant  is  shown  by  Fig.  4. 

This  plant,  which  occupies  a  floor  of  25'  x  50',  was  designed  for 
use  where  the  old-fashioned  method  of  pickling  sandy  castings 
with  sulphuric  acid  was  to  be  employed.  A  small  plant  of  this 
kind  could  be  put  in  a  much  smaller  floor  space.  In  floor  plan 
Fig.  4,  A  is  a  tank  for  containing  a  solution  of  sulphuric  acid  and 
water  for  removing  scale  and  rust.  B  is  a  water  tank  for  storing 
work  that  has  been  cleaned.  C  is  a  platform  where  castings  are 
placed  to  free  them  from  sand  with  the  use  of  sulphuric  acid.  D  is 
a  tank  used  to  contain  the  solution  for  removing  the  sand  from 
the  castings  after  they  have  been  placed  on  the  platform.  E  is  a 
tank  for  containing  muriatic  acid.  F  is  the  plate  for  drying  the 
work  before  immersing  it  in  the  molten  metal.  G  is  the  kettle 
containing  the  metal,  and  H  is  the  tank  used  for  cooling  the  work 
after  it  is  coated  with  the  zinc.  I  I  indicate  the  loose  planks 
covering  the  ash  pits,  shown  in  Fig.  11  as  P  P.  K  is  an  under- 
ground flue  connecting  the  drying  plate  F  with  the  chimney  or 
stack  L;  and  M  is  a  pit  to  give  access  to  the  ash  pit  under  the 
drying  plate  F. 

The  Equipment 

The  equipment  of  a  galvanizing  plant  for  miscellaneous  work 
consists  of  a  kettle  of  suitable  size,  which  should  be  built  of  the 
very  best  material  obtainable;  a  drying  "arch,"  "plate"  or  "oven" 
for  drying  the  castings  prior  to  immersing  them  in  the  molten 
zinc;  wooden  tanks  for  containing  water  and  the  different  acid 
solutions;  and  miscellaneous  tools  best  adapted  to  the  work  in 
hand,  such  as  tongs,  hooks  and  baskets  of  perforated  sheet  iron  or 
wire  cloth.  Considerable  ingenuity  can  be  exercised  in  devising 
implements  for  handling  the  various  kinds  of  work.  \Ve  shall 
refer  to  this  matter  of  tools  later  under  a  special  head. 

The  material  used  in  the  construction  of  galvanizing  kettles  and 
tools  which  come  in  contact  with  the  molten  spelter  is  a  matter  of 
great  importance.  In  this  connection,  the  statement  of  the  super- 


18  GALVANIZING  AND  TINNING 

intendent  of  one  of  the  largest  sheet  galvanizing  plants  in  the 
country  is  interesting,  and  we  give  it  herewith. 

The  endeavor  to  find  the  most  suitable  material  for  manu- 
facturing those  parts  of  the  machinery  which  are  immersed  in 
spelter,  as  well  as  the  best  container  for  the  molten  spelter,  has 
occupied  the  attention  of  galvanizers  for  all  time.  The  only  sub- 
stances which  are  not  dissolved  are  vitreous,  and  consequently,  im- 
practical. All  of  the  common  metals  are  soluble  in  molten  zinc, 
and  all  of  them  are  miscible  in  all  porportions,  with  the  exception 
of  lead  and  iron.  For  this  reason,  and  because  of  the  many  other 
desirable  properties  which  iron  possesses,  it  is  universally  used  at 
the  present  time. 

The  old  galvanizers  made  their  machinery  of  wrought  iron; 
but  with  the  introduction  of  Bessemer  and  open  hearth  steel  have 
quite  generally  adopted  this  material,  because  it  possesses  certain 
very  distinct  advantages  over  wrought  iron.  It  does,  however,  go 
into  solution  much  more  rapidly  than  the  old  wrought  iron  did; 
so  that  for  the  last  ten  years  the  search  has  been  for  a  material 
which  will  work  as  well  as  steel  does,  and  resist  the  solvent  action 
as  well  as  the  iron. 

The  laws  of  physics  teach  us  that  an  impure  substance  will  go 
into  solution  more  rapidly  than  a  pure  one,  and  we  do  not  find 
exceptions  when  dissolving  iron  in  zinc.  The  purer  the  iron  the 
more  slowly  it  goes  into  solution.  This  is  the  reason  that  the 
old-fashioned  puddled  iron  lasted  so  much  longer  than  the  modern 
steel.  Now  that  ingot  iron  is  being  commercially  produced,  it  has 
been  very  easy  to  demonstrate  this  fact  in  a  scientific  manner. 

In  a  recent  investigation  the  following  facts  were  disclosed: 
Sixteen  gauge  samples  of  various  analysis  were  suspended  in  molten 
spelter  for  twelve  days  with  the  following  results: 

Armco  Iron  Steel  Steel 

Sulphur                                     .032  .036  .022 

Phosphorus                              .008  .067  .006 

Carbon                                      .010  .045  .010 

Manganese                               .017  .372  .145 

Silicon  trace  trace  trace 

Copper                                     .048  trace  .192 

Loss  in  12  days  11.2%  40.9%  27.00% 

Having  satisfactorily  demonstrated  that  there  was  a  very  marked 
difference  between  pure  iron  and  steel  (impure  iron),  another  set 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT 


19 


of  experiments  was  conducted  to  bring  out  the  difference  in  the 
effect  between  slight  variations  in  very  pure  iron.  Samples  of  the 
following  analysis  were  used,  and  were  suspended  for  four  hun- 
dred fifty  hours  (three  150  hour  periods). 


1 

2 

3 

4 

5 

Silicon 

trace 

trace 

trace        trace 

trace 

Sulphur 

.022 

.025 

.025 

.026 

.027 

Phosphorus 

.003 

.004 

.003 

.003 

.005 

Carbon 

.015 

.04 

.015 

.01 

.10 

Manganese 

.02 

.005 

.04 

.01 

.065 

Copper 

..045 

.035 

.11 

.11 

Oxygen 

.015 

.017 

.025 

.041 

.03 

Total    Impurity 

.120 

.126 

.218 

.200 

.227 

Iron    by    difference 

99.88 

99.874 

99.782 

99.80 

99.773 

Loss   in   450   hours 

34.4% 

38.5% 

42.0% 

55.7% 

(41.5%  loss  in 

300  hours.  ) 

Average  weight  of  coating  in  150  hours 

370 

314     272 

248     212 

It  will  be  noticed  that  the  rate  of  solution  increases  directly  in 
proportion  to  the  amount  of  impurity.  These  specimens  were  all 
weighed  very  carefully,  were  totally  immersed  in  spelter,  not  com- 
ing in  contact  with  the  salammoniac  flux  at  any  time ;  the  coating 
being  stripped  off  with  sodium  hydroxide,  which  dissolves  the 
spelter  but  does  not  attack  the  iron.  From  these  results  it  is  evi- 
dent that  while  dealing  with  commercially  pure  iron  it  is  essential 
to  secure  the  very  purest.  A  material  containing  99.84%  iron 
being  much  better  than  one  containing  only  99.75%  iron.  You 
will  note  also  that  the  rate  of  solution  increases  with  the 
amount  of  oxygen;  showing  the  additional  necessity  of  securing  a 
thoroughly  degassified  and  deoxidized  material. 

Another  interesting  fact  to  be  noticed  in  the  table  given  above 
is  that  the  weight  of  coating  taken  on  varies  inversely  as  the  rate  of 
solution:  that  is,  the  more  rapidly  the  material  dissolves,  the 
lighter  coating  it  takes  on. 

These  facts  as  worked  out  in  the  laboratory  are  very  interest- 
ing, but  needed  verification  in  actual  practice  before  they  could 
be  of  any  real  importance  to  the  galvanizer.  For  this  reason,  all 
parts  of  the  galvanizing  machine  under  the  spelter,  in  one  manu- 
facturer's plant,  were  manufactured  of  Armco  Iron.  He  finds  that 
cast  Armco  Iron  lasts  just  about  as  long  as  rolled  or  forged  10 
carbon  steel;  whereas  Armco  Iron,  properly  worked  and  heat 


20  GALVANIZING  AND  TINNING 

treated,  will  last  from  three  to  seven  times  as  long  as  mild  steel 
will.  Flux  boxes,  for  example,  lasting  from  eight  to  ten  months. 

These  statements  are  borne  out  and  given  additional  weight  by 
a  comparison  of  galvanized  Armco  Iron  sheets  with  galvanized 
mild  open  hearth  steel  sheets.  The  iron  content  of  a  clean  spelter 
bath  is  approximately  .02%.  Any  iron  in  excess  of  this  forming 
dross,  and  settling  to  the  bottom.  The  coating  on  Arruco  Iron 
sheets  contains  about  3%  iron,  while  the  coating  on  steel  sheets 
contains  about  4% ;  showing  very  definitely  that  even  in  the  short 
time  that  the  sheets  are  in  the  spelter  bath,  steel  goes  into  solution 
much  more  rapidly. 

It  is  a  source  of  great  satisfaction  to  know  that  a  material  is 
being  commercially  produced,  which  lasts  even  longer  in  the 
spelter  than  the  old-fashioned  wrought  iron,  and  at  the  same  time 
possesses  all  the  excellent  working  qualities  of  steel. 

The  Selection  of  a  Kettle 

In  deciding  what  size  kettle  to  install  one  must  be  guided  by  the 
nature  and  quantity  of  work  to  be  done.  If  small  articles  are  to 
be  handled,  and  the  quantity  is  such  as  to  require  the  plant  to  be 
operated  only  at  intervals,  a  kettle  3  feet  long,  15  or  18  inches 
wide  and  20  inches  deep  will  answer  every  purpose,  but  it  is  ex- 
tremely difficult  to  keep  an  even  temperature  of  the  metal  in  a 
kettle  of  this  size.  The  only  excuse  for  using  such  a  small  kettle 
is  for  doing  an  extremely  limited  amount  of  work  as  a  matter  of 
convenience,  with  cost  as  a  secondary  consideration. 

Bricking  in  a  Galvanizing  Kettle 

There  are  several  methods  of  heating  galvanizing  kettles.  Some 
are  heated  with  soft  coal,  some  with  fuel  oil  and  some  with  natural 
gas.  The  fuel  most  commonly  used,  however,  is  coke.  For  this 
reason  we  shall  show,  by  illustrations,  three  methods  of  bricking 
in  coke-fired  kettles.  We  do  not  attempt  to  describe  any  particu- 
lar method  of  oil  or  natural  gas  heating,  as  concerns  using  either 
fuel  usually  have  their  own  methods  of  application. 

Figs.  5,  6  and  7  show  methods  of  setting  a  small  kettle  not 
deep  enough  to  require  ash  pits  at  the  sides  and  not  designed  to  be 
operated  continually.  The  grates  F  F  are  bars  of  iron  that  may 
be  withdrawn  when  it  is  desired  to  let  the  fires  out,  and  replaced 
when  required  for  use.  Fig.  5  is  a  top  plan  of  the  brick  work  and 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT 


21 


kettle.     Fig.  <>   is  a  vertical  cross  section  of  Fig.  5  at  A  A,  and 
Fig.  7  is  a  horizontal  section  of  Fig.  6  at  B  B. 


FIG.  5 — PLAN  OF  KETTLE 


Section  B-B 

FIG.  7 — ARRANGEMENT  AT  GRATE  LINE 


Sect/on A- A 

FIG.  6 — VERTICAL  CROSS  SECTION  OF  FURNACE  AND  KETTLE 

Fig.  8  shows  the  casting  details  for  setting  kettle  as  shown  in 
Figs.  5,  6  and  7.  D  is  a  plate  to  cover  top  of  brick  work  surround- 
ing the  kettle,  and  its  position  is  designated  in  Fig.  5  as  D  D. 
E  is  a  casting  used  on  outside  of  brick  work  on  both  sides  of  kettle 
and  in  connection  with  bolts  passing  through  their  ends  serve  to 
bind  the  brick  work  together.  Their  position  is  designated  in 
Fig.  6  as  E  E.  F  is  a  grate  bar,  the  position  of  which  is  shown 
in  Fig.  7  at  F  F,  and  G  G  are  the  castings  for  supporting  each 
end  of  the  grate  bars  F.  Their  position  is  designated  as  G  G  in 
Figs.  6  and  7.  The  castings  for  the  upper  and  lower  draft  hole 
casings  with  doors,  designated  as  II  and  I  in  Figs.  5  and  6,  can 
be  made  the  same  as  castings  K,  L,  M  and  N  in  Fig.  13. 


22 


GALVANIZING  AND  TINNING 


B    O 


.  g — CASTING  DETAILS  FOR  SETTING  KETTLE 


0-A 


O   -A 


FIG.  9 — TOP  PLAN  OF  BRICKWORK  FOR  LARGER  KETTLE 


FIG.  10— SIDE  ELEVATION  OF  THE  SAME  KETTLE 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT 


23 


Figs.  9,  10,  11  and  12  show  manner  of  setting  larger  kettles 
where  grates  are  used ;  Fig.  9  being  a  top  plan  of  the  brick  work ; 
Fig.  10  a  side  elevation;  Fig.  11  a  vertical  section  at  A  A;  Fig.  9 
and  Fig.  12  a  horizontal  section  at  the  grate  line. 


FIG.  11 — VERTICAL  CROSS  SECTION  OF  KETTLE  AND  FURNACE 


FIG.  12 — HORIZONTAL  SECTION  AT  THE  GRATE  LINE 

Fig.  13  gives  details  of  all  castings  necessary  for  setting  all 
grate-fired  kettles,  as  shown  in  Figs.  9,  10,  11  and  12.  A,  Fig.  13, 
is  a  coping  plate,  the  position  of  which  is  shown  in  Figs.  9,  10 
and  11  as  A  A.  These  plates,  when  held  in  place  by  the  bolts  C, 
serve  to  prevent  the  sides  of  the  kettle  from  springing  outward 
when  the  iron  blocks  D,  Fig.  13,  are  in  their  place,  as  shown  in 


24 


GALVANIZING  AND  TINNING 


Figs.  9  and  11.  Coping  plates  for  kettles  4  to  6  ft.  long  should  be 
Scinches  thick  and  10  inches  wide.  The  fire  spaces  E  E  in  Figs.  9 
and  1 1  should  not  be  more  than  7  inches  wide,  and  the  same  length 
as  the  inside  of  the  kettle.  F  in  Fig.  13  is  an  iron  plate  1  inch  thick, 
and  the  position  of  these  plates  on  the  brick  work  is  shown  as 
F  F  in  Figs.  9  and  11.  G  in  Fig.  13  is  a  section  of  grate,  the 
position  of  which  is  designated  G  G  in  Figs.  11  and  12.  The 
openings  of  these  grates  should  be  about  "1  inch  wide,  and  the 


3S 

u 

FIG.  13 — DETAILS  OF  CASTING 


SI:TT:NG  G::ATE-FIKED  KETTLE 


grates  should  be  wide  enough  to  span  the  fire  spaces  E  E  in  Figs.  9 
and  11  and  rest  on  plates  H  H  and  the  pier  I  on  which  the  kettle 
B  rests,  as  shown  in  Fig.  11.  Plates  like  H  in  Fig.  13  are  used 
to  rest  the  outer  edge  of  the  grates  G  G  on,  as  shown  in  Figs.  11 
and  12,  and  also  to  help  support  the  brick  walls  on  each  side  of 
the  kettle.  Plates  such  as  H  in  Fig.  13  may  also  be  used  to  cover 
the  top  of  fire  boxes  E  E  in  Figs.  9  and  11,  and  should  be  about 
24  inch  thick  and  12  inches  wide;  their  length  to  be  determined  by 
the  length  of  the  kettle.  K  in  Fig.  13  is  a  cast  iron  casing  for  the 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT 


25 


upper  draft  holes,  indicated  as  K  K  in  Figs.  10  and  11.  These 
casings  should  be  about  10  inches  long  with  openings  about  4  by 
4  inches.  They  should  also  be  arranged  to  close  with  sliding  doors 
L,  as  shown  at  L,  Fig.  10.  M  in  Fig.  13  shows  a  cast  iron  casing 
for  the  lower  set  of  draft  holes  in  which  the  openings  should  be 
about  8  by  12  inches.  Their  position  in  the  brick  work  is  desig- 
nated M  in  Figs.  10,  11  and  12.  N  in  Fig.  13  is  a  sliding  door 
for  the  draft  hole  casings  M,  and  they  are  designated  N  in  Figs. 
10  and  11.  0  in  Fig.  13  is  a  cast  iron  foundation  washer  which 
is  built  in  the  brick  work  on  the  bottom  ends  of  the  vertical 
bolts  C.  The  ash  pits  P  P,  Fig.  11,  should  be  about  2  feet  wide 
and  covered  with  loose  floor  planks  so  that  easy  access  may  be  had 
to  the  ash  pits  for  the  purpose  of  opening  or  closing  the  lower 


FIG.  14 — PLAX  AXD  ELEVATIONS  OF  KETTLE 

drafts,  and  also  for  removing  the  ashes  from  the  spaces  R  R  under 
the  grates  G  G.  Fig.  12  shows  the  grates  G  G  in  position,  and 
also  the  manner  of  laying  the  bricks  between  the  draft  oasings  M  M. 
I  indicates  the  pier  on  which  the  kettle  rests.  It  will  be  seen  that 
the  brick  work  between  the  lower  draft  casings  M  M  is  built  in  a 
way  which  will  allow  all  possible  access  to  the  grates  G  G  from  the 
ash  pits  P  P.  The  walls  along  each  side  of  the  kettle  should  have 
a  lining  of  fire  brick  extending  from  the  grates  upward  to  the 
coping  plates  A  A,  as  shown  in  Fig.  11. 

Fig.  11  shows  a  kettle  in  which  the  body  is  formed  of  one  piece, 
with  rivets  placed  where  the  fire  will  not  affect  them.  While  a 
kettle  for  general  use  built  after  this  illustration  is  our  preference 
for  many  reasons,  it  does  not  follow  that  the  work  could  not  be 
done  in  a  kettle  of  some  other  shape. 


26 


GALVANIZING  AND  TINNING 


Figs.  15,  16  and  17  show  the  setting  of  kettles  fired  without 
grates  and  with  only  one  set  of  draft  holes.    Fig.  15  is  a  sectional 


FIG.  1.1 — SECTION*  OF  BRICKWORK  AND  KETTLE  AT  A  A,  FIG.  17 

plan  of  the  brick  work  and  kettle  through  17  at  A  A.  Fig.  16  is  a 
sectional  side  elevation  through  Fig.  15  at  B  B.  Fig.  17  is  a  sec- 
tional end  elevation  through  Fig.  15  at  C  C. 


FIG.  16— SIDE  ELEVATION  AT  B  B.  FIG.  15 

Figs.  18  to  23  show  construction  of  a  simple  and  effective  ar- 
rangement for  drying  castings  previous  to  dipping  them  in  the 
molten  zinc.  Fig.  18  is  a  side  elevation  of  a  "drier"  showing 


&• 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT 


27 


furnace  front  with  fire  and  ash  pit  doors.    Fig.  19  is  a  longitudinal 
section  of  Fig.  22  at  C  C.     Fig.  20  is  a  lateral  section  of  Fig.  22 

\ 


"    ..     " 


K 


Jl     ..      IL 


l_-^^^s^^ 


"        .   " 


FIG.  17 — SECTION  AT  C  C,  FIG.  15 


z> 

'  " 


FIG.  18 — GENERAL  VIEW  OF  FURNACE  rou  DRYING  CASTINGS 

at  A  A.     Fig.  21  is  a  lateral  section  of  Fig.  22  through  B  B, 
showing  ash  pits  and  grates.     Fig.  22  is  a  longitudinal  section  of 


28 


GALVANIZING  AND  TINNING 


Fig.  21  through  D  D,  and  shows  arrangements  of  flues.  Fig.  23  is 
a  longitudinal  section  of  Fig.  21  through  E  E,  and  shows  grate 
and  fire  box  with  fire  brick  lining. 

We  give  the  method  of  setting  kettles  with  and  without  grates 
for  the  reason  that  there  is  a  diversity  of  opinion  as  to  which  is 


Secfton   C-C 


FIG.  10 — LONGITUDINAL  SECTION  AT  0  C,  FIG.  22 


""""""'  B 


Sect/on  *-A 
FIG.  20 — CROSS  SECTION  AT  A  A,  FIG.  22,  SHOWING  FLUES 

the  better  method.  "Without  discussing  this  matter  pro  or  con,  the 
author  will  simply  say  that  he  prefers  a  kettle  fired  without  grates. 
Some  claim  that  a  grate  fired  kettle  lasts  much  longer  than  one 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT 


Secf/on  e-3 

FIG.  21 — VERTICAL  SECTION  THROUGH  B  B,  FIG.  22,  SHOWING  FURNACE 
AND  FLUES 


FIG.  22— PLAN  OF  DRIER,  SHOWING  Tor  FLUES  AT  D  D,  FIG.  21 


30 


GALVANIZING  AND  TINNING 


set  without  grates,  as  without  grates  the  draft  comes  directly  onto 
the  side  of  the  kettle,  which  results  in  burning  it  out  much  quicker 
than  would  otherwise  be  the  case. 


FIG.  23 — PLAN  SHOWING  GRATE  AND  FIRE  Box  AT  E  E,  FIG.  21 

Tanks  for  Acid  Solutions  and  Water 

In  our  opinion,  the  best  lumber  for  acid  tanks  is  cypress,  al- 
though some  prefer  the  different  varieties  of  pine.  Most  galvaniz- 
ers  use  wooden  tanks  for  containing  the  cooling  and  rinsing  waters. 
Water  tanks  made  of  boiler  iron  will  give  very  good  service,  in 
fact  they  are  more  economical  than  wooden  water  tanks.  Wooden 
tanks  for  holding  the  various  acid  solutions  should  invariably  be 
put  together  with  copper  bolts,  nuts  and  washers,  and  it  is  a  good 
plan  to  line  the  inside  of  such  tanks  with  rough  boards  that  can 
be  replaced  when  worn  out.  These  linings  protect  the  inside  of 
the  tanks  and  will  increase  their  life  very  materially.  It  will  be 
found  a  good  plan  to  coat  the  inside  of  wooden  tanks  intended  for 
cold  acid  with  asphaltum.  The  asphaltum  should  be  heated  as 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT 


31 


hot  as  possible  without  danger  of  its  catching  fire  and  put  on 
thickly  with  an  old  broom.  When  asphaltum  is  used  in  this  way 
it  is  absolutely  necessary  to  protect  it  with  a  rough  board  lining 
such  as  mentioned  above. 

It  was  formerly  considered  necessary  to  line  acid  tanks  with 
sheet  lead,  but  of  late  years  this  is  rarely  done,  as  the  use  of  lead 
linings  makes  the  maintenance  of  acid  tanks  a  very  serious  item 
of  expense.  If  the  tanks  are  properly  constructed  there  is  no 
necessity  for  lining  with  lead. 


FIG.  24 — PLAN  AND  ELEVATIONS  or  ACID  TANK 

Fig.  24  shows  a  good  method  for  constructing  wooden  tanks. 
It  is  unnecessary  to  build  expensive  tanks  for  a  small  plant  that 
is  only  to  be  run  at  irregular  intervals.  Oil  barrels  sawed  in  half, 
thoroughly  cleaned,  answer  every  purpose,  provided,  of  course,  the 
work  is  of  a  size  which  half  barrels  will  accommodate.  In  build- 
ing acid  tanks  one  must  be  guided  entirely  by  requirements  in 
determining  size. 

Tools  for  Galvanizing 

The  tools  employed  in  galvanizing  usually  consist  of  tongs  of 
various  shapes  and  sizes,  dependent  entirely  on  the  shape  of  the 
articles  to  be  handled.  Perforated  baskets  of  sheet  iron  for  gal- 
vanizing small  articles,  and  baskets  made  from  heavy  wire  cloth 
can  be  used  to  good  advantage  for  a  great  many  purposes,  as  can 
wires  bent  in  various  shapes.  As  already  suggested  under  a  previ-. 


.32 


GALVANIZING  AND  TINNING 


ous  heading,  a  great  deal  of  ingenuity  may  be  exercised  in  con- 
structing special  tools  for  the  handling  of  work  of  various  shapes. 
In  Fig.  25  we  show  a  few  of  the  most  common  implements  that 
serve  as  tools  for  the  handling  of  a  variety  of  work.  A  shows  a 
basket  made  of  wire  cloth,  attached  to  an  iron  handle  of  suitable 
length,  preferably  from  3£  to  4  feet.  B  is  a  perforated  basket 


FIG. 


N    <  i  ALVAMZING 


made  of  sheet  iron.  This  tool  is  necessary  for  dipping  small  ar- 
ticles, such  as  nails,  tacks,  screws  and  many  other  articles  too  small 
to  be  handled  otherwise.  Several  of  the  baskets,  A  and  B,  should 
be  provided  for  use  when  wanted.  C  is  a  tool  made  of  common 
round  iron  bent  in  the  form  of  a  letter  U.  This  tool  is  useful  for 
immersing  in  the  molten  metal  articles  too  large  to  be  immersed 
in  baskets.  D  is  also  used  for  dipping  small  articles  that  can  be 
handled  in  this  way  better  than  in  baskets.  D  is  made  of  wire  of 
suitable  size,  and  it  is  a  good  plan  to  have  at  least  a  dozen  each 
of  C  and  D  for  use  when  required.  E  and  F  are  skimmers.  The 
bowl  of  F  is  made  of  No.  16  or  No.  18  gauge  sheet  iron  and 
perforated  with  :|  inch  holes.  Tt  should  be  provided  with  a  handle 
at  least  4  feet  in  length,  and  the  bowl  should  be  about  8  inches  in 
diameter.  The  blade  of  E  should  be  made  of  a  piece  of  No.  16 


HOT  GALVANIZING  PLANT  AND  EQUIPMENT  33 

gauge  sheet  iron  from  1  to  6  inches  in  length  by  2  inches  in  width. 
The  handle  should  be  made  of  f  or  £  inch  round  iron,  from  15  to 
18  inches  in  length.  G  is  a  tool  used  for  suspending  castings  in 
the  galvanizing  bath  that  are  strung  on  wires.  It  should  be  made 
of  f  or  f  inch  round  iron,  and  be  from  4£  to  5  feet  in  length. 
11  is  a  scoop  for  removing  dross  from  the  galvanizing  kettle.  The 
use  of  all  these  tools  will  be  referred  to  in  describing  the  different 
operations  of  galvanizing. 


CHAPTER  III 

The  Pyrometer 

THE  author  has  had  many  inquiries  regarding  the  use  of  a 
pyrometer  in  a  galvanizing  kettle.  While  it  has  not  been  his 
practice,  or  generally  the  practice  of  other  galvanizers,  to 
depend  on  the  pyrometer  to  any  great  extent,  preferring  that  the 
operator  should  school  himself  to  determine  the  proper  heat  of  the 
metal  by  observation,  the  introduction  of  improved  instruments  for 
determining  more  accurately  actual  temperatures  is  undoubtedly 
making  converts  to  new  and  better  methods. 

While  a  reliable  pyrometer  is  without  question  an  advantage  to 
the  hot  galvanizer,  it  can  never  replace  the  skilled  operator.  The 
reason  is  obvious.  In  the  first  place,  hardly  any  two  brands  of 
spelter  will  give  the  same  results  at  the  same  temperature.  Then 
again,  different  classes  of  work  require  widely  different  tempera- 
tures of  the  galvanizing  bath.  If  gray  iron  castings  were  to  be 
galvanized  a  temperature  proper  for  some  other  classes  of  work 
would  be  found  altogether  too  high.  "Where  a  kettle  is  used  for 
miscellaneous  work  it  is  necessary  to  change  the  temperature  of 
the  metal  several  times  a  day.  In  such  cases  I  have  found  a 
pyrometer  of  very  little  use.  A  pyrometer  is  an  advantage  on 
straight  work,  such  as  sheets,  wire  cloth,  etc.,  etc.,  or,  in  fact,  any 
class  of  work  that  is  run  continuously  day  after  day.  A  good 
pyrometer  placed  in  the  kettle  from  time  to  time  is  of  great  as- . 
sistance  to  the  operator,  however  skilful  he  may  be,  and  it  is  also 
of  great  advantage  in  caring  for  the  kettle  at  night  and  at  other 
times  when  not  in  operation. 

When  the  ordinary  style  of  pyrometer  is  used  the  stem  should 
be  protected  from  the  action  of  the  zinc  or  it  will  soon  be  de- 
stroyed. A  means  by  which  the  stem  of  the  pyrometer  is  kept 
from  contact  with  the  molten  zinc,  at  the  same  time  giving  the 
same  result  as  if  in  actual  contact,  is  shown  in  detail  by  Fig.  27. 
The  arrangement  consists  of  a  piece  of  2-inch  pipe  about  20  inches 
long  with  one  end  tightly  closed.  The  top  of  the  pipe  is  provided 
with  a  bushing  having  a  hole  a  little  larger  in  diameter  than  the 

34 


THE  PYROMETER  35 

stem  of  the  pyrometer.  A  similar  bushing  is  placed  in  the  pipe 
about  3  inches  from  the  bottom  and  the  two  serve  to  keep  the 
pyrometer  in  an  upright  position.  The  pipe  surrounding  the  stem 
of  the  pyrometer  is  filled  with  lead  so  that  when  the  apparatus  is 
placed  in  the  kettle  there  is  a  direct  metallic  connection  between 
the  stem  of  the  pyrometer  and  the  molten  zinc.  Pig.  26  shows 
such  a  pyrometer  in  position  in  the  kettle. 


FIG.  26 — CORRECT  POSITION  OF  PYROMETER  IN  FURNACE 

The  importance  of  maintaining  a  safety  point  in  the  temperature 
of  the  hot  galvanizing  bath  is  recognized  by  everyone,  and  the  ques- 
tion has  received  the  attention  of  practical  and  scientific  men.  A 
paper  presented  before  the  Mechanical  Section  of  the  Engineers' 
Society  of  Western  Pennsylvania  in  1912,  by  S.  H.  Stupakoff  of 
Pittsburgh,  puts  this  matter  so  concisely  and  intelligently  that  I 
have  asked  and  received  the  permission  of  the  gentleman  to  use 
the  paper  in  the  production  of  this  book.  Mr.  Stupakoff  says  as 
follows : 

Considerable  difficulty  is  encountered  in  galvanizing  practice  to 
keep  the  temperature  of  the  molten  metal  within  the  limits  which 
produce  a  clean  and  uniform  coating  on  the  surface  of  articles 
treated  by  this  process.  The  most  suitable  galvanizing  tempera- 
ture lies  usually  about  50  deg.  Fahr.  above  the  melting  point  of  the 
metal  bath.  Ten  or  fifteen  degrees  either  way  may  result  in  in- 
ferior products.  The  melting  point  of  pure  zinc  is  787  deg.  Fahr. 
Impurities  or  other  metals,  such  as  lead,  antimony,  aluminum,  etc., 


36 


GALVANIZING  AND  TINNING 


intentionally  added,  or  accidentally  occurring  in  the  mixture,  usu- 
ally lower  the  melting  point;  and  in  such  a  case  it  will  be  found 
preferable  to  lower  the  galvanizing  temperature  accordingly.  This 
makes  us  conclude  that  the  temperatures  of  galvanizing  baths  re- 
quire close  watching.  Ten  degrees  above  or  below  850  deg.  Fahr. 
is  very  little ;  it  would  escape  the  notice  of  the  best  of  us,  unless  we 


FIG.  27 — DEVICE  FOR  PROTECTING  PYROMETER 

were  guided  by  the  most  reliable  instruments.  It  lies  beyond  the 
region  of  the  human  senses.  We  may  be  able  to  distinguish  a 
difference  of  10  or  15  deg.  above  or  below  65  deg.  Fahr.  when 
sitting  quietly  at  our  studies,  feeling  uncomfortably  cold  at  50 
or  55  deg.  or  uncomfortably  warm  at  75  or  80  deg.,  but  that  is 
about  our  limit. 

This  would  indicate  that  our  metals  are  far  more  sensitive  to 
small  variations  of  temperature  than  the  human  body.  And  more 
so,  if  we  consider  that  10  deg.  difference  at  65  represents  about 
15  1/3  per  cent.,  whereas  10  deg.  at  850  is  less  than  1  1/5  of  1 
per  cent.  Unaided  by  trustworthy  temperature  measuring  instru- 
ments it  will  always  remain  an  extremely  difficult  matter,  even 
for  an  expert,  to  make  an  approximate  estimate  of  conditions. 
Though  it  is  conceded  that  the  phenomena  invariably  accompany- 
ing changes  of  temperature,  if  intelligently  interpreted,  may  lead 


THE  PYROMETER  37 

to  a  successful  conclusion  of  metallurgical  processes,  it  cannot  be 
denied  that  whatever  they  may  involve  they  depend  upon  the  per- 
sonal equation,  which  cannot  be  tolerated  in  modern  manufacturing 
practice. 

We  receive  in  this  manner  undisputable  indications  of  the  condi- 
tions of  the  fluid  metal  in  galvanizing  practice  through  the  forma- 
tion of  dross,  the  degree  of  intensity  of  its  coloring,  the  behavior 
of  the  flux,  the  intricate  motions  on  the  skimmed,  clean  surface 
of  the  metal  accompanied  by  the  appearance  of  variously  shaped 
crystals,  like  ice  crystals  on  a  Avindow  pane,  and  most  of  all  through 
the  appearance  of  the  metallic  coating  of  the  galvanized  products 
themselves. 

They  may  remain  forever  an  enigma  to  the  uninitiated,  whereas 
a  man  who  has  spent  a  lifetime  at  this  task  may  have  finally  mas- 
tered the  problem.  Nevertheless  it  is  not  a  rare  occurrence  that 
a  galvanizing  tank  in  the  hands  of  an  expert  operator  gives  out 
after  a  few  months ;  and  replacing  it  is  always  a  very  costly  mat- 
ter. The  cause  in  ninety-nine  cases  in  a  hundred  is  overheating 
the  metal. 

As  it  is  very  important  that  a  constant  temperature  be  main- 
tained in  the  bath,  reliable  instruments  should  be  provided  that  will 
indicate  the  temperature  correctly.  This  is  far  more  difficult  than 
ordinarily  assumed.  It  may  be  appreciated  to  some  extent  if  the 
assertion  of  a  friend,  who  has  had  wide  experience  in  this  direction, 
be  accepted  as  descriptive  of  the  average  general  conditions  in 
recent  galvanizing  practice.  He  assured  me  that  he  had  tried  many 
heat  measuring  instruments  during  the  last  twenty  years,  and  that 
not  one  had  given  satisfaction.  Some  failed  because  they  were 
too  fragile,  others  because  they  were  unreliable  from  the  beginning, 
some  because  they  were  inconstant  and  changing  in  time,  and  still 
others  because  they  were  erratic  in  their  indications.  The  last  of 
these,  which  undoubtedly  embraces  the  majority  of  instruments 
of  the  kind,  is  the  least  tolerable  of  the  lot.  Instead  of  imparting 
confidence,  they  give  just  cause  to  distrust,  and  they  invite  ridicule 
of  the  workingmen  to  whom  they  are  represented  as  infallible.  I 
have  often  run  against  freaks  of  this  kind.  Few  of  them  would 
indicate  the  correct  temperature  within  50  or  100  deg.  Some  would 
run  along  smoothly  for  a  while,  and  then  drop  300  or  400  degrees 
within  a  half  or  three-quarters  of  an  hour  and  rising  again  as 
quickly.  Judging  from  the  series  of  lassitudes  and  occasional 


38  GALVANIZING  AND  TINNING 

sudden  spurts  of  activity,  they  represented  anything  but  existing 
conditions.  Now,  what  faith  could  a  man  have  in  such  an  erratic 
indicating  device,  if  he  knows  that  a  tank  containing  from  10  to 
15  tons  of  molten  zinc  will  not  cool  more  than  19  or  20  deg.  Fahr. 
per  hour  with  all  the  fires  turned  off?  Let  me  give  an  example 
taken  from  actual  practice. 

The  temperature  of  a  galvanizing  tank,  containing  about  240,000 
Ibs.  of  zinc,  dropped  170  deg.,  from  850  to  G80  deg.  Fahr.  in  27 
hours,  after  the  gas  fires  were  shut  off.  This  would  indicate  an 
average  cooling  of  only  six  degrees  and  a  fraction  per  hour,  which 
is  less  than  a  third  of  the  maximum  drop  that  has  just  been 
mentioned. 

Melting  point  of  zinc  (M.  P.) 419.5°  C. 

Specific  heat  of  liquid  zinc  (S) 0.1275 

Mean  specific  heat  of  solid  zinc   (from  o°  to 

t°)    (S.M.)    0.0906 -(- 0.000044t 

Mean  specific  heat  before  fusion  at  M.  P 0.109058 

Heat  in  solid  metal  at  M.  P.   (from  above)   45.75  Calories 

Heat  in  solid  metal  at  M.  P.   (Richards)   45.20  Calories 

Heat  in  liquid  metal  at  M.  P.  (Person) 67.80  Calories 

Latent  heat  of  fusion   (observed)    22.60  Calories 

Latent  heat  of  fusion   (by  2.1  T  rule) 22.40  Calories 

Latent  heat  of  fusion   (from  above)   22.05  Calories 

Galvanizing  temperature  (about) 455°  C 

Heat  required  to  raise  liquid  metal  from  M.   P.  to 

455°   C 4.5  Calories 

Total  heat  in  liquid  metal  at  455°  C 72.3  Calories 

Total  heat  in  liquid  metal  at  455°  C 130.14  B.  t.  u. 

The  latent  heat  of  fusion  of  zinc  per  pound  (Cal.) 22.6 

Heat  in  molten  metal  at  850  deg.  Fahr.  is  (Cal.) 72.26 

and  at  680  deg.,  to  which  it  had  been  cooled  (Cal.) 38.28 

hence  it  has  parted  at  680  deg.  with  (Cal.) 33.94 

Distributed  over  the  27  hours,  cooling,  this  is  about  l1/^  cal. 
per  Ib.  hr.  for  the  whole  mass  of  24,000  Ib.  is  about 

(Cal.  per  Ib.  hr.) 300000 

Deducting  from  the  above   (Cal.) 33.94 

The  latent  heat  (Cal.) 22.6 

there  remains  almost  exactly  1/3   (Cal.) 11.34 

which  should  be  evenly  distributed  over  9  hours,  which  is 
1/3  of  the  total  time  of  cooling;  the  remaining  2/3,  or  18 
hours,  were  consumed  to  turn  the  liquid  metal  into  a  solid 
mass.  Dividing  170,  the  total  drop  in  temperature  by  9, 
the  time  in  hours,  we  find  19,  or,  say,  roundly  20  deg. 
Fahr.  drop  per  hour. 


THE  PYROMETER  39 

The  freezing  of  the  metal  should  have  commenced  accord- 
ingly, after  (hours)    3 

it  would  have  been  solid  throughout  after  (hours) 21 

and  the  temperature  would  have  dropped  during  the  (hours) . .  .6 
remaining,  at  a  fairly  even  rate  per  hour  of  (deg.  Fahr.) . .  .20 

This  is  a  rough  illustration  of  what  takes  place  in  practice.  The 
finer  shades  of  variations  have  been  purposely  omitted  in  this  cal- 
culation to  save  complications.  The  observations  cited  were  made 
during  the  winter  months;  the  thermometer  indicating  about  30 
or  35  deg.  Fahr.  Changes  in  atmospheric  conditions  would  cause 
considerable  change  in  the  results,  as  the  heat  lost  by  the  molten 
metal  is  given  up  to  the  surrounding  air  principally  by  conduction 
and  convection.  Differences  in  temperature  and  movement,  draft, 
of  the  air  would  be  the  most  important  factors  in  such  changes. 

The  question  is  often  asked  whether  reliable  test  thermometers 
can  be  obtained  for  the  purpose.  Undoubtedly  they  are  to  be  had, 
but  there  should  be  no  occasion  to  use  them  for  checking  other  in- 
struments of  their  kind,  if  such  convenient  and  reliable  means  can 
be  used  as  the  freezing  point  of  the  metal  itself.  We  have  no  reason 
to  find  fault  with  our  commercial  thermometers.  The  better  grade 
can  be  relied  upon  to  be  correct  within  one-half  of  a  division,  even 
without  a  certificate;  but  most  confusing  results  can  be  obtained 
with  a  thermometer,  especially  with  a  long  stem  thermometer,  if 
it  is  not  correctly  used.  Ordinary  commercial  thermometers  are 
graduated  to  be  used  at  full  immersion ;  that  is,  not  only  the  bulb, 
but  also  the  entire  mercury  column  is  to  be  exposed  to  the  tempera- 
ture which  is  to  be  measured.  However,  full  immersion  is  a  con- 
dition seldom  met  with  when  a  thermometer  is  used  for  technical 
purposes.  In  most  instances  only  a  portion  of  the  stem  can  be 
immersed  into  the  heated  medium,  and  unless  the  thermometer  has 
been  especially  constructed  for  the  purpose,  grave  errors  will  result. 
Otto  Bechstein  says  in  his  description  of  "Instruments  for  the  meas- 
uring of  temperatures  in  technical  pursuits"  that  this  error  may 
amount  to  50  deg.  Cent.,  and  more  in  long-stem  thermometers.  I 
must  confess  that  this  is  more  than  I  have  ever  had  occasion  to 
observe ;  but,  notwithstanding  this,  he  may  be  right.  As  ridiculous 
as  it  may  seem,  it  appears,  therefore,  quite  appropriate  to  recom- 
mend to  users  that  they  learn  the  proper  use  of  a  thermometer,  and, 
furthermore,  when  purchasing  to  fully  describe  the  requirements. 

It  would  seem  that,  if  such  apparently  simple  devices  as  indus- 


40  GALVANIZING  AND  TINNING 

trial  thermometers  require  the  amount  of  care  in  their  construction 
and  application  as  has  here  been  described,  other  types  of  heat- 
measuring  instruments,  which  command  more  extended  ranges  and 
which  see  a  more  severe  use,  can  scarcely  be  expected  to  be  entirely 
free  from  objectionable  features.  Each  type  has  its  scope,  each 
must  be  used  with  due  care  and  with  each  set  rules  must  be  intelli- 
gently observed  to  obtain  satisfactory  results  in  their  application. 

The  most  important  features  of  some  of  them  have  been  referred 
to;  it  was  impossible  to  enter  into  the  details  of  all  the  instru- 
ments, nor  could  all  their  useful  application  in  the  large  number 
of  processes  of  the  metal  industries  be  described  at  length  in  a 
paper  of  necessarily  limited  length.  To  cover  the  entire  ground 
would  fill  a  large  volume  and  require  a  series  of  lectures.  The 
discussion  of  the  subject  may  bring  forth  many  points  of  interest 
which  have  not  been  mentioned. 


CHAPTER  IV 

Materials  Used  in  Hot  Galvanizing 

THE  materials  used  in  galvanizing  are  slab  zinc  (spelter), 
pig  lead,  white  and  gray  granulated  sal  ammoniac,  zinc 
ammonium  chloride,  muriatic,  sulphuric  and  hydrofluoric 
acids,  coke    (if  side  fired   kettles   are  used),  oil,  glycerine,   and 
aluminum  properly  mixed  for  fluxing  metal. 

Spelter 

We  cannot,  with  fairness,  express  a  preference  for  any  particular 
brand  of  spelter;  but  on  general  principles  we  do  recommend  the 
use  of  Virgin  spelter  smelted  by  a  reliable  firm.  We  do  not  recom- 
mend the  use  of  what  is  commercially  known  as  "Kemelt"  spelter 
by  those  who  are  not  familiar  with  this  metal.  While  most  Re- 
melt  spelter  is  run  down  from  sheet  zinc,  there  are  several  brands 
on  the  market  which  have  been  recovered  from  zinc  dross  by  those 
who  have  not  the  facilities  for  properly,  doing  the  work.  We  do 
not  wish  to  go  on  record  as  claiming  it  impossible  to  recover  good 
metal  from  zinc  dross.  In  fact,  we  have  in  mind  a  brand  of  spelter 
that  is  recovered  from  zinc  dross  which  gives  as  good  results,  both 
in  quality  of  the  work  and  economy,  as  the  best  brands  of  Virgin 
spelter.  Great  progress  has  been  made  in  the  last  few  years  toward 
the  recovery  of  galvanizing  by-products  of  all  kinds,  and  materials 
at  one  time  considered  worthless  and  consigned  to  the  waste  heap 
are  now  valuable. 

No  infallible  rule  by  which  the  layman  may  determine  the 
quality  of  spelter  can  be  given.  The  only  positive  way  is  by  an- 
alysis. In  a  general  way  the  quality  of  spelter  may  be  determined 
fairly  well  by  breaking  slabs  and  observing  the  fracture.  If  the 
fracture  shows  a  bright,  regular  and  large  granular  face  it  indi- 
cates that  the  spelter  is  of  good  quality,  but  if  the  fracture  shows 
dark,  small  granules  it  indicates  quality  that  is  not  the  best.  A 
magnifying  glass,  when  applied  to  a  freshly  broken  slab  of  Remelt 
spelter,  will  often  reveal  small  black  particles  acting  as  wedges  be- 
tween the  granules.  These  particles  are  foreign  matter  prin- 
cipally, and  therefore  lessen  the  value  of  the  spelter  as  well  as 

41 


42  GALVANIZING  AND  TINNING 

acting  as  a  detriment  in  melting  and  coating  operations.  How- 
ever, if  the  policy  of  buying  only  Prime  Western  or  Virgin  spelter 
is  followed,  one  can  be  sure  that  no  dross  is  introduced  into  the 
galvanizing  bath  in  the  spelter,  as  would  be  the  case  if  Remelt 
spelter,  reclaimed  by  crude  methods  from  zinc  dross,  was  used. 

Lead 

Scrap  lead  will  answer  every  purpose  for  use  in  the  galvanizing 
kettle  as  described  under  the  heading  "Filling  a  New  Kettle," 
but  if  it  is  necessary  to  procure  pig  lead  for  this  purpose  it  is  best 
to  buy  what  is  known  as  "hard  lead." 

White  and  Gray  Granulated  Sal  Ammoniac 

These  chemicals  play  an  important  part  in  the  process  of  hot 
galvanizing;  the  grade  known  as  "gray  granulated"  sal  ammoniac 
being  used  to  form  a  flux  on  the  surface  of  the  zinc,  which  flux  is 
necessary  to  facilitate  the  proper  coating  of  the  work  and  to  re- 
tard the  oxidation  of  the  molten  zinc  by  excluding  the  air.  White 
sal  ammoniac  is  used  to  sprinkle  on  the  surface  of  the  molten  metal 
as  the  work  is  withdrawn.  Some  galvanizers  use  the  white  for 
both  purposes.  These  chemicals  are  an  important  item  of  expense 
in  the  cost  of  hot  galvanizing  and  care  should  be  exercised  against 
buying  inferior  grades.  The  best  sources  of  supply  can  only  be 
learned  by  experience,  as  it  would  be  manifestly  out  of  place  for 
the  author  to  express  a  preference  in  this  book  for  the  product  of 
any  particular  manufacturer  located  either  in  this  country  or 
abroad. 

Zinc  Ammonium  Chloride 

The  use  of  zinc  ammonium  chloride  on  the  galvanizing  bath 
as  a  substitute  for  gray  granulated  sal  ammoniac  is  comparatively 
a  new  idea.  As  a  matter  of  fact,  it  is  only  used  at  this  writing 
by  comparatively  few  galvanizers.  We  give  it  the  preference  over 
gray  granulated  sal  ammoniac,  not  by  reason  of  economy,  but  from 
the  standpoint  of  comfort.  The  fumes  of  zinc  ammonium  chloride 
rising  from  the  surface  of  the  molten  zinc  are  less  disagreeable  to 
the  operator  and  less  destructive  than  the  fumes  of  sal  ammoniac, 
and,  in  our  opinion,  it  gives  much  better  results  than  the  sal 
ammoniac. 


MATERIALS   USED   IX   HOT   GALVANIZING  43 

Muriatic,  Sulphuric  and  Hydrofluoric  Acids 

These  acids  are  readily  obtainable  in  all  important  trade  centers 
and  are  so  common  that  no  extended  reference  regarding  them  is 
necessary. 

Coke 

Coke  is  the  only  practicable  fuel  that  can  be  used  on  kettles  of 
the  character  shown  in  the  preceding  pages.  While  it  is  possible 
to  use  what  is  known  as  foundry  coke  for  heating  a  galvanizing 
kettle,  it  is  unsatisfactory,  and  the  best  results  are  obtained  with 
that  produced  in  making  illuminating  gas,  commonly  known  as 
gas  coke,  which  may  usually  be  purchased  at  a  lower  figure. 

Oil 

Oil  is  commonly  used  in  the  galvanizing  process  on  the  surface 
of  the  water  in  which  the  work  is  cooled  after  it  has  been  taken 
from  the  molten  zinc.  While  some  galvanizers  use  different  grades 
of  fuel  oil,  we  have  found  that  better  results  are  obtained  by  using 
what  is  known  as  "mineral  lard  oil." 

Glycerine 

Glycerine  is  used  in  a  small  plant  in  very  limited  quantities. 
Therefore,  the  small  operator  can  depend  on  his  local  druggist  for 
what  is  necessary.  In  large  plants  it  is  usually  bought  from  the 
manufacturers  in  iron  drums  holding  from  ten  to  twelve  hundred 
pounds. 

Aluminum 

This  metal  is -quite  commonly  used  in  galvanizing  baths  to  make 
the  metal  more  fluid  and  improve  the  appearance  of  the  work.  Its 
use  has  become  so  common  that  several  concerns  now  make  a  busi- 
ness of  manufacturing  aluminum  alloys  or  fluxing  metals  for 
galvanizing  purposes,  selling  them  under  various  trade  names.  The 
different  manufacturers  of  these  alloys  have  their  own  methods  of 
application ;  consequently,  we  shall  not  attempt  to  give  any  hard 
and  fast  rules  for  the  use  of  fluxing  metals  in  a  galvanizing  bath. 


CHAPTER  V 

Pickling 

A  THE  first  operation  in  any  process  of  galvanizing  or 
tinning  is  to  properly  prepare  the  work  to  take  the  coating, 
we  will  give  that  our  first  attention  by  describing  the  dif- 
ferent methods.  Many  large  concerns  use  the  mechanical  pickling 
apparatus  shown  in  Figs.  28  and  29. 

There  are  several  agencies  that  may  be  employed  in  preparing 
work  for  galvanizing.  Sulphuric,  muriatic  and  hydrofluoric  acids 
are  all  valuable  agents  for  this  purpose,  and  the  ones  most  com- 
monly employed. 

The  cleaning  of  work  with  acids  preparatory  to  coating  them 
by  any  process  is  known  as  "pickling."  Pickling  means  the  re- 
moval of  scale  and  other  foreign  substances  from  the  surface  of 
the  metals  by  the  chemical  action  of  the  acid.  If  the  material  to 
be  cleaned  is  simply  soaked  in  acid  the  chances  are  that  too  much 
of  the  metal  will  be  dissolved,  as  the  action  is  not  uniform  on 
account  of  the  varying  density  of  the  acid,  and  the  cleaning  is  both 
uncertain  and  uneven.  Agitation  is  therefore  desirable.  This  was 
originally  and  still  is  to  a  great  extent  accomplished  by  hand,  al- 
though many  of  the  large  manufacturers  of  galvanized  sheets,  gal- 
vanized wire,  galvanized  pipe,  tin  plate,  cold  rolled  steel  and  cold 
rolled  shafting  employ  mechanical  methods  to  procure  proper 
agitation  of  the  material  in  the  pickling  vats  because  hand  pickling 
of  these  materials  was  always  insufficient  and  inefficient.  As  a 
pickling  macbine  brings  mechanical  action  into  play  to  the  extent 
that  the  material  is  pickled  with  about  one-half  of  the  acid  and 
labor  required  in  hand  pickling,  we  consider  it  our  duty  to  refer 
to  it  in  this  article  as  well  as  to  illustrate  it.  The  best  result  is 
obtained  by  moving  the  material  being  cleaned  through  the  acid 
with  a  predetermined  velocity.  By  proper  mechanical  means  the 
sheets  (if  such  are  being  pickled)  are  separated  and  shifted  suffi- 
ciently to  allow  the  acid  to  enter  between  them  and  prevent  their 
sticking  together.  The  acid  washing  over  the  surface  has,  in  con- 
junction with  the  loosened  particles  of  scale,  a  scouring  action 
which  thoroughly  cleans  the  sheets.  The  uniform  action  of  the 

44 


PICKLING 


acid  upon  the  surface  is  assisted  by  thoroughness  of  the  agitation, 
which  does  not  allow  acid  layers  of  different  density  to  form.  In 
pickling  sheets  this  feature  is  of  extreme  importance.  If  they  are 


FIG.  28 — VIEW  OB-  MKCHANICAL  PICKLING  EQUIPMENT 

immersed  in  a  vat  of  improperly  agitated  acid,  layers  of  varying 
density  form  so  that  before  the  upper  parts  of  the  plates  are  prop- 
erly pickled  the  lower  parts  are  over-pickled.  The  above  is  also 
true  with  regard  to  the  cleaning  of  pipe  by  mechanical  means.  If 


46 


GALVANIZING  AND  TIXXIXG 


pipe  that  is  intended  for  galvanizing  is  kept  in  agitation  in  the 
acid  vat  by  mechanical  means,  the  cost  of  acid  and  labor  is  ma- 
terially reduced  and  the  work  much  better  done. 

While  mechanical  pickling  methods  have  not  been  applied  to  any 
great  extent  to  the  cleaning  of  castings  or  other  small  articles,  they 
might  be  applied  to  marked  advantage  in  many  cases,  and  the  ideal 
mechanical  method  is  one  that  keeps  the  material  being  pickled  in 
motion  instead  of  one  that  simply  agitates  the  acid. 


FIG.  29 — A  SECTION  SHOWING  ARRANGEMENT  OF  MECHANICAL  PICKLER 

Acid  consumption  per  ton  of  material  depends  upon  many  cir- 
cumstances. Purity  and  strength  of  acid,  temperature  of  the 
pickle,  thickness  of  scale,  etc.,  govern  acid  consumption. 

The  pickling  of  certain  classes  of  material,  mainly  sheets  for 
tinning  or  galvanizing,  is  technically  known  as  "black  pickling" 
and  "white  pickling."  Black  pickling  means  the  removal  of  the 
heavy  oxide  formed  during  the  hot  rolling  process.  White  pickling 
means  the  removal  of  the  film  of  oxide  resulting  from  the  second 
annealing.  To  have  the  work  properly  done,  acid  must  wash  over 
all  the  surfaces  all  the  time;  otherwise,  as  before  stated,  the  ma- 
terial is  not  pickled  uniformly.  In  pickling  sheets  for  galvanizing 
or  tinning  the  change  from  one  acid  vat  to  another  must  consume 


PICKLING  47 

very  little  time;  otherwise,  the  product  will  accumulate  dry  acid 
and  oxide. 

What  we  have  said  thus  far  regarding  pickling  applies,  of  course, 
more  particularly  to  large  plants  than  to  the  ordinary  jobbing 
plant  handling  miscellaneous  work.  \Ve  will,  therefore,  treat  the 
subject  from  the  standpoint  of  ordinary  requirements,  as,  in  ad- 
dition to  acids  for  preparing  work  for  galvanizing  and  tinning, 
we  have  the  rolling  barrel  and  the  sand  blast,  both  of  which  can 
l)e  employed  to  good  advantage,  especially  the  sand  blast.  Acids, 
however,  are  an  absolute  necessity,  while  the  rolling  barrel  and  the 
sand  blast  are  simply  valuable  auxiliary  agents. 

Removing  Scale  with  Sulphuric  Acid 

Articles  of  sheet  iron  or  steel  arc  covered  to  a  greater  or  less 
extent  with  scale,  which  must  be  removed  completely  before  zinc 
will  adhere  to  them.  To  accomplish  the  removal  of  this  scale,  and 
also  the  removal  of  rust,  solutions  composed  of  sulphuric  acid  and 
water  of  different  degrees  of  strength  are  employed.  Probably  a 
solution  composed  of  one  part  sulphuric  acid  to  twenty  parts  of 
water,  reckoned  by  weight,  at  a  temperature  of  150  degrees  F., 
will  answer  for  as  great  a  variety  of  requirements  as  any,  although 
the  strength  and  temperature  of  the  solution  may  be  safely  varied 
in  the  hands  of  a  skilled  operator.  The  trouble  to  be  guarded 
against  is  over-pickling,  by  which  we  mean  subjecting  the  material 
to  a  solution  that  is  too  strong,  or  too  hot,  or  for  too  long  a  time. 
The  effect  of  over-pickling  is  apparent,  as  it  results  in  leaving  the 
material  full  of  seams,  or  when  it  happens  to  work  that  has  been 
threaded,  in  the  entire  or  partial  destruction  of  the  threads. 

The  length  of  time  required  to  accomplish  the  work  varies  with 
the  thickness  of  the  scale.  In  many  cases  it  is  necessary  to  re- 
move thick  spots  of  scale  with  some  sharp-pointed  tool.  The  shank 
of  an  old  file  sharpened  and  hardened  answers  this  purpose  very 
nicely.  Patches  of  heavy  scale  are  often  found  rolled  into  the 
heavier  gauges  of  sheet  iron  and  steel,  and  they  are  nearly  always 
present  on  forged  work.  As  that  part  of  the  article  first  becom- 
ing cleaned  by  the  action  of  the  acid  would  be  injured  if  allowed 
to  remain  in  the  acid  long  enough  to  remove  the  heavy  scale  it  is 
necessary  to  use  a  tool  of  some  sort  to  loosen  the  spots  of  heavy 
scale.  Material  having  an  uneven  coating  of  scale  should  be  cleaned 
in  a  weaker  solution  than  that  having  an  even  coating  or  that 


48  GALVANIZING  AND  TINNING 

having  a  light  scale.  The  reason  is  that  the  part  of  the  stock  which 
is  first  cleaned  will  be  over-pickled  before  the  parts  having  the 
heavier  scale  are  clean. 

Where  large  quantities  of  wrought  iron  and  steel  products  are 
pickled  or  cleaned  with  sulphuric  acid,  which  must  be  heated  to 
perform  its  function  to  best  advantage,  the  fumes  arising  from  the 
pickling  solutions  are  very  obnoxious  and  the  conditions  in  the 
pickling  rooms,  and  sometimes  adjacent  departments,  in  some  of 
the  large  plants  are  almost  unbearable,  especially  in  the  late  fall, 
winter  and  early  spring. 

With  the  view  of  overcoming  the  objectionable  features  of  sul- 
phuric acid,  without  at  the  same  time  sacrificing  efficiency  or  add- 
ing considerably  to  expense,  several  substitutes  for  pickling  and 
cleaning  wrought  iron  and  steel  have  been  placed  on  the  market 
in  recent  years. 

"Kleanrite"  is  referred  to  by  the  manufacturers  as  a  "powdered 
compound,  soluble  in  water."  Its  use  requires  no  change  in  the 
pickling  equipment.  It  is  used  in  a  solution  made  up  of  1  pound 
of  "Kleanrite"  to  4  or  5  pounds  of  water,  or  may  be  varied  to  suit 
any  particular  or  unusual  conditions  in  pickling.  For  quick  re- 
sults the  solution  is  heated  to  150  to  200  degrees  F.  It  is  claimed 
to  pickle  without  burning,  and  without  pitting  the  metal.  It  does 
not  exhale  any  disagreeable  or  destructive  fumes  such  as  are  pres- 
ent when  pickling  with  sulphuric  acid. 

"Edis  Compound"  is  another  substitute  for  pickling  acid.  It  is 
manufactured  in  the  form  of  dry  cakes  Avhich  are  simply  dissolved 
in  water  and  brought  up  to  about  200  degrees  temperature;  in 
other  words,  it  is  used  just  about  the  same  as  acid,  but  being  in 
the  dry  cakes  it  is  very  convenient  and  pleasant  to  handle,  and  does 
not  start  to  act  on  anything  until  it  is  dissolved  in  water. 

When  the  work  has  been  pickled  free  from  scale  and  rust  and 
is  perfectly  clean,  it  should  be  stored  for  future  use  in  a  tank  con- 
taining water  enough  to  cover  it  completely.  A  in  Fig.  3  desig- 
nates the  tank  to  be  used  for  pickling  the  material  to  remove 
scale,  and  B  in  the  same  illustration  denotes  the  storage  tank. 

Eust  and  scale  may  be  removed  by  the  aid  of  muriatic  acid, 
properly  diluted  with  water,  although  not  as  economically  as  with 
sulphuric  acid,  but  in  cases  where  only  small  quantities  of  forg- 
ings  or  articles  made  from  sheet  iron  or  steel  are  handled  the  sul- 
phuric acid  solution  can  be  dispensed  with  entirely  and  the  operator 


PICKLING  49 

can  use  the  muriatic  acid  solution  exclusively.  A  safe  "pickle"  of 
muriatic  acid  is  one  part  acid  to  four  parts  water,  liquid  measure. 
If  it  should  be  desirable  to  hasten  the  cleaning  process  when  using 
the  muriatic  solution  it  may  be  heated  to  a  temperature  of  150 
degrees  F.,  although  the  material  must  be  carefully  watched  to 
prevent  over-pickling. 

Cleaning  Sandy  Castings  with  Sulphuric  Acid 

Castings  that  are  sandy  may  be  cleaned  by  pouring  over  them 
a  cold  solution  of  sulphuric  acid  and  water,  one  part  acid  to  six  of 
water.  Place  the  castings  on  an  inclined  platform  and  wet  them 
frequently  with  the  solution.  Continue  this  operation  until  the 
sand  is  loosened,  when  the  castings  should  be  removed  and  water 
dashed  over  them  to  remove  all  loose  sand.  This  process  is  gen- 
erally known  as  "foundry"  pickling,  and  was  extensively  used  at 
one  time.  Castings  that  have  been  subjected  to  this  treatment  too 
long  will  be  covered  with  what  appears  to  be  a  gummy  or  greasy 
substance,  and  will  not  take  the  coating  of  zinc  properly  unless 
they  are  left  in  the  metal  a  long  time,  and  even  then  they  will  not 
be  nicely  coated,  but  will  be  rough  and  covered  with  thick  patches 
of  metal.  They  will  not  have  the  smooth  finish  which  properly 
prepared  castings  have. 

Cleaning  Castings  with  the  Aid  of  Hydrofluoric  Acid 

Hydrofluoric  acid  has  come  into  almost  general  use  among  gal- 
vanizers  for  the  removal  of  sand.  There  is  very  little  danger  of  its 
injuring  the  iron,  and  as  it  dissolves  sand  readily,  it  is  the  ideal 
acid  agent.  We  have  subjected  an  extremely  sandy  casting  to  the 
action  of  a  cold,  weak  solution  of  hydrofluoric  acid  for  3  or  4  days 
before  the  sand  was  entirely  dissolved  without  any  perceptible  in- 
jury to  the  casting  itself.  Many  galvanizers  bring  the  temperature 
of  their  hydrofluoric  pickle  to  anywhere  from  75  to  200  degrees  F. 
We  believe  that  it  is  a  serious  mistake  to  make  this  a  common 
practice.  There  are  occasions  when  it  is  absolutely  necessary  that 
the  work  be  accomplished  in  the  quickest  possible  time;  but  as  a 
general  rule  plenty  of  time  may  be  taken  for  the  removal  of  the 
sand,  and  it  is  done  much  better  and  more  economically  and  satis- 
factorily by  the  use  of  a  weak,  cold  solution.  In  our  regular  work 
we  employ  sufficient  tank  capacity  to  permit  of  the  castings  re- 
maining in  a  weak,  cold  solution  from  8  to  24  hours.  Castings 


50  GALVANIZING  AND  TINNING 

prepared  this  way  for  galvanizing  will  take  the  zinc  readily,  cause 
the  formation  of  less  dross  in  the  galvanizing  kettle,  and  have 
much  better  commercial  appearance  than  castings  prepared  quickly 
in  a  hot,  strong  solution.  A  solution  composed  of  one  part  acid 
to  ten  parts  water  has  very  little  tendency  to  injure  the  iron  if 
used  cold,  although  we  often  allow  the  solution  in  our  tanks  to 
fall  much  below  this  strength.  As  a  matter  of  fact,  we  make  up  a 
new  solution  only  at  long  intervals,  simply  adding  a  little  acid  and 
a  little  water  from  time  to  time  as  necessary.  We  have  found  this 
formula  very  efficient  for  a  quick  pickle : 

Hydrofluoric  acid  (30%),    6  gallons 
Muriatic  acid,  4       " 

Water,  40       " 

This  solution  should  be  used  warm,  not  hot.  The  action  of  the 
muriatic  acid  hastens  the  removal  of  the  sand,  but  is  not  violent 
enough  to  injure  the  casting. 


CHAPTER  VI 

Water  Rolling,  Tumbling  and  Sand  Blasting 

THERE  are  many  times  when  the  tumbling  barrel  will  be 
found  of  great  value  in  the  cleaning  process;  especially  in 
a  plant  devoted  to  miscellaneous  work  or  to  the  galvanizing 
of  malleable  or  gray  iron  castings.  It  not  only  facilitates  the 
process  of  removing  sand  from  such  castings,  but  can  be  employed 
to  good  advantage  in  removing  heavy  rust  or  scale  from  forgings; 
thus  overcoming  to  a  great  extent  the  danger  of  over-pickling,  as 
well  as  the  disagreeable  features  connected  with  the  use  of  acids. 
Castings  of  a  character  that  permit  of  their  being  tumbled  can 
often  be  put  in  proper  shape  to  receive  the  zinc  coating  without 
subjecting  them  to  the  action  of  acid,  and,  in  any  event,  castings 
that  have  been  tumbled  only  require  a  short  time  in  an  extremely 
weak  solution  of  hydrofluoric  acid. 

Water  Rolling 

A  piece  of  wrought  iron  from  which  the  scale  has  been  removed 
by  the  use  of  acid  will  not  have  the  smooth  and  perfect  coating 
that  it  would  have  if  the  scale  was  removed  by  rolling.  The  same 
is  true  of  malleable  iron  castings.  The  best  and  most  perfect  re- 
sults are  obtained  by  giving  the  castings  a  thorough  tumbling  in 
gravel  and  water,  which  operation  brings  their  surface  to  a  state 
of  smoothness  only  equaled  by  buffing  or  polishing.  Malleable 
castings  on  which  it  is  desired  to  obtain  a  fine  finish  should  in- 
variably be  given  this  treatment.  It  is  also  necessary  that  patterns 
from  which  castings  are  made  that  are  designed  to  be  tinned 
should  be  finished  to  produce  the  smoothest  surface  possible.  This 
will  help  to  shorten  the  tumbling  operation. 

Some  tinners  not  only  roll  their  castings  in  gravel  and  water, 
but  for  the  purpose  of  obtaining  a  smoother  surface  than  can  be 
obtained  by  this  method  they  roll  them  with  scraps  of  leather,  the 
entire  operation  often  requiring  30  or  40  hours.  Water  rolling  is 
so  common  and  so  thoroughly  understood  that  we  consider  it  un- 
necessary to  give  detailed  instructions  regarding  the  apparatus  to 
be  used  or  the  methods  employed.  There  are  several  concerns  who 

51 


52  GALVANIZING  AND  TINNING 

make  the  manufacture  of  rolling  barrels  for  this  purpose  a  spe- 
cialty, and  the  cheapest  method  to  adopt  when  equipping  a  tinning 
plant  with  wet  rolling  barrels  is  to  buy  the  outfit  complete  from  a 
manufacturer  who  has  made  a  study  of  the  business. 

Dry  Tumbling 

Iron  castings  as  they  come  from  the  foundry  always  have  more 
or  less  sand  upon  them  and  castings  of  large  size  or  peculiar  shape 
often  have  patches  or  pockets  of  sand  burnt  into  their  surface, 
which  cannot  readily  be  removed  by  pickling.  One  cheap  and 
efficient  way  of  removing  this  sand  is  by  dry  "tumbling,"  and  this 
method  has  been  used  for  years  by  iron  foundries  to  clean  their 
castings,  and,  at  the  same  time,  to  improve  their  appearance  by 
brightening  and  smoothing  their  surfaces,  therefor  dry  tumbling 
serves  two  important  purposes,  cleaning  and  polishing,  and  all 
who  are  familiar  with  foundry  practice  are  more  or  less  familiar 
with  tumbling.  There  are  several  types  of  dry  tumbling  barrels 
on  the  market  made  by  different  manufacturers,  but  most  of  them 
are  cylindrical  in  form  and  the  most  improved  outfits  are  designed 
to  be  fitted  with  a  system  of  pipes  and  fan  for  removing  dust  from 
the  barrels.  This  dust  would  otherwise  go  off  in  the  room  and 
is  sometimes  quite  objectionable. 

Most  castings  are  of  such  shape  that  they  could  not  be  thor- 
oughly cleaned  or  polished  in  the  tumbling  barrel,  unless  some 
smaller  objects  were  tumbled  with  them,  which  would  work  into 
the  holes  or  identations  on  their  surface.  For  this  purpose  iron 
stars,  commonly  called  jack  stones,  diamonds  or  cubes  are  used, 
all  of  which  in  foundry  parlance  are  called  "shot."  Very  small 
castings  with  fairly  smooth  surfaces  can  oftentimes  be  tumbled 
clean  without  the  use  of  shot. 

To  load  a  tumbling  barrel  put  in  first  a  thin  layer  of  shot  and 
then  a  layer  of  castings  and  continue  in  this  manner,  one  layer 
upon  another,  until  the  barrel  is  nearly  filled.  Some  space  must  be 
left  for  the  castings  and  shot  to  move  about  in  as  the  barrels  re- 
volve. The  friction  caused  by  this  moving  or  ''tumbling"  cleans 
the  castings.  If  fragile  gray  iron  castings  are  being  tumbled,  too 
much  space  must  not  be  left  in  the  barrel,  as  such  castings  would 
be  broken  by  the  shock  of  tumbling  with  too  much  force.  One- 
third  shot  and  two-thirds  castings  (by  bulk)  is  about  the  right 
proportion  for  ordinary  tumbling,  but  the  proportion  should  be 


WATER  ROLLING,  TUMBLING  AND  SAND  BLASTING          53 


changed  to  suit  the  individual  requirements  of  each  lot  of  castings 
using  more  shot  for  hollow  castings,  or  castings  with  a  very  uneven 
surface  and  less  for  plain  castings  with,  comparatively  smooth  sur- 
faces. After  the  barrel  is  loaded  and  started  very  hard  pounding 
of  its  contents  will  warn  the  operator  that  the  barrel  is  not  prop- 
erly packed  and  castings  may  be  injured  if  allowed  to  £pntinue 
tumbling  under  these  conditions. 

In  tumbling  for  galvanizing  let  the  castings  remain  in  the  barrel 
until  all  sand  possible  is  removed  without  injuring  them,  as  this 
is  the  most  important  object  of  tumbling  for  galvanizing.  Practice 
makes  perfect  and  with  intelligent  study  of  the  problem  an  opera- 
tor can,  after  a  time,  tumble  castings  so  clean  that  they  will  require 
very  little,  if  any,  pickling  before  galvanizing.  The  cleaning  of 
many  kinds  of  work  for  galvanizing  is  greatly  simplified  by  the  use 
of  the  tumbling  barrel.  Old  rusty  chains  and  castings  or  wrought 
iron  forgings  which  are  badly  rusted  can  usually  be  cleaned  to  good 
advantage  in  this  way.  Old  paint  can  also  be  removed  fromi  arti- 
cles which  can  be  tumbled  much  easier  and  better  in  many  cases 
by  tumbling  than  by  any  other  means.  In  addition  to  cleaning 
cheaply,  tumbling  also  makes  the  surface  of  castings  smooth,  which 
greatly  improves  the  appearance  of  the  galvanizing. 

The  Wet  Tumbling  Barrel 

The  barrel  is  constructed  in  accordance  with  the  plan  shown  in 
Figs.  30A,  30B  and  30C.  The  points  where  in  this  barrel  differs 
from  the  ordinary  wet  rolling  barrel  are:  that  it  is  built  very 
heavy  and  strong,  is  provided  with  valves  for  the  escape  of  gases 
generated  by  the  chemi- 
cals used,  and  the  open- 
ing where  the  barrel  is 
tilled  is  arranged  to  close 
tightly. 

For  general  work  we 
prefer  a  barrel  48  inches 
long  and  24  inches  in 
diameter.  The  shell  we 

make    of    i-inch    boiler' 

,    "  FIG.  30A— TUMBLING  BARBEL 

iron,  and   use   cast   iron 

heads  H  inches  thick.  The  manhole  cover  we  make  1  inch  thick, 
and  have  it  well  ribbed  to  give  additional  strength. 


54 


GALVANIZING  AND  TINNING 


Fig.  SOB  is  a  plan  view  of  the  barrel,  and  it  also  shows  the 
receiving  tank  IT,  designated  in  the  ground  plan,  Fig.  51,  as  B. 

Fig.  30A  is  an  elevation  of  Fig.  30B. 

Fig.  30C  gives  the  details  of  the  barrel,  in  which  A  is  an  end 
view  of  the  trunnions  B  and  C,  and  D  is  a  view  of  the  pillow 
blocks  supporting  the  barrel,  and  E  is  the  pillow  block  for  the 
pinion  shaft;  F  is  a  valve  for  the  escape  of  gas,  and  G  is  a  view 
of  the  end  of  the  barrel  on  which  the  valves  F  are  placed,  while 
H  shows  the  rolling  barrel  cover. 

Preparing  the  Castings  for  the  Tumbling  Barrel 

The  details  of  cleaning  having  been  carefully  attended  to,  place 
the  castings  in  the  tumbling  barrel,  together  with  a  quantity  of 
ordinary  iron  "stars,"  such  as  used  in  dry  tumbling,  being  care- 
ful to  load  the  barrel  in  such  a  way  as  to  prevent  breaking  or 
wearing  the  corners  of  the  castings.  Tea  kettles  should  be  filled 
full  of  stars  or  shot  before  placing  them  in  the  tumbling  barrel, 
and  light,  delicate  castings  should  be  packed  tightly  enough  to 
prevent  breaking.  Stars  or  shot  sufficient  to  fill  the  barrel 
about  one-fourth  full  will  be  found  the  most  desirable  quan- 
tity for  ordinary  work, 
although  on  hollow  ware 
much  more  are  needed, 
or  enough  to  fill  up 
nearly  all  the  vacant 
space.  After  the  barrel 
has  been  loaded  in  the 
way  described,  put  in 
water  sufficient  to  fill  it 
about  three-fourths  full, 
then  add  15  pounds  of 
commercial  muriatic  acid 
and  2  pounds  of  gray 
granulated  sal  ammo- 
niac. The  barrel  is  now 
ready  to  be  closed  and 

started,  presuming  that  the  operator  has  examined  the  valves  to 
see  that  they  are  in  perfect  working  order  previous  to  loading  the 
barrel. 

After  the  barrel  has  been  in  motion  from  5  to  15  minutes,  de- 


FIG.  30B — TOP  VIEW  OF  TUMBLING  BARBEL 


G.  Imhoff 


WATER  ROLLING,  TUMBLING  AND  SAND  BLASTING          55 

pending  on  the  temperature  of  the  water  used,  there  will  be  formed 
sufficient  gas  to  cause  the  valves  to  open.  The  escape  of  gas  will 
be  accompanied  by  quantities  of  the  solution,  and  the  end  of 
the  barrel  on  which  the  valves  are  placed  should  be  inclosed,  un- 
less the  barrel  is  set  up  in  a  room  itself. 

The  time  which  castings  should  be  rolled  in  this  solution  varies 
from  2i  to  5  hours.  Soft,  smooth  castings  will  take  a  nice  coat- 
ing after  a  rolling  of  2£  hours,  while  to  obtain  the  same  results 
on  hard  iron,  iron  cleaned  by  the  use  of  sulphuric  acid,  hollow 
ware  and  tea  kettles  and  castings  having  a  black  lead  facing,  5 
or  more  hours  in  the  barrel  may  be  necessary.  It  is  safe  to  say 
that  3£  hours  is  sufficient  to  properly  roll  ordinary  castings  if  the 
barrel  turns  40  revolutions  a  minute.  For  hollow  ware,  tea  ket- 
tles and  very  delicate  castings  the  barrel  should  not  attain  a 
speed  of  over  30  revolutions  per  minute.  After  the  castings  have 
been  rolled  in  the  solution  the  required  time,  open  the  barrel 
and  cover  its  contents  with  water  immediately.  Do  not  let  time 
be  wasted  in  getting  the  castings  covered  with  water,  as  a  slight 
exposure  to  the  air  will  cause  them  to  oxidize  and  prevent  them 
from  taking  the  tin.  If  the  castings  are  properly  prepared — that 
is,  if  they  have  been  rolled  in  the  solution  long  enough — they  will 
be  in  such  condition  after  rinsing  that  they  will  not  soil  a  white 
cloth,  rubbed  on  their  surface,  to  any  extent. 

Should  it  be  found  that  the  castings  are  not  properly  prepared 
(which  is  done  by  putting  one  or  two  of  the  pieces  through  the 
regular  treatment),  the  barrel  should  be  re-charged  by  adding  6 
pounds  of  muriatic  acid  and  allowed  to  run  about  an  hour  longer. 
In  rolling  castings  plans  should  be  made  to  complete  the  work 
before  the  stopping  of  the  power  at  noon  and  night.  3£  hours 
being  required  on  an  average  to  prepare  iron  in  the  rolling  bar- 
rel, it  is  easy  to  arrange  to  start  the  barrel  in  time  to  complete 
one  batch  in  the  morning  and  one  in  the  afternoon.  This  would 
furnish  work  enough  to  keep  two  hands  engaged,  although  one 
set  of  kettles  would  take  care  of  all  the  iron  that  could  be  pre- 
pared in  a  barrel  of  the  size  we  show;  viz.,  2  feet  in  diameter 
by  4  feet  in  length. 

If  the  castings  are  quite  soft  and  clean  three  batches  may  be 
prepared  in  ten  hours,  in  which  case  the  second  batch  should  be 
in  the  barrel  in  time  to  give  it  at  least  one  hour's  rolling  before 
the  power  is  stopped  at  noon.  When  a  batch  of  iron  is  left  in 


66 


GALVANIZING  AND  TINNING 


the  barrel  during  the  noon  hour,  leave  the  barrel  closed,  and  in  a 
position  where  one  of  the  valves  will  be  up,  with  its  opening  above 
the  solution  in  the  barrel.  Unless  this  is  done  the  valves  may 
open  and  allow  the  solution  to  escape,  necessitating  the  re-charging 
of  the  barrel.  If  a  batch  of  castings  is  not  completed  in  season, 
to  remove  it  to  the  storage  tank  before  the  time  for  stopping  the 


flfl     fl 


FIG.  30c — DETAILS  OF  TUMBLING  BARREL  EQUIPMENT 

power  at  night,  remove  the  cover,  and  allow  enough  fresh  water 
to  flow  into  the  barrel  to  displace  at  least  half  of  the  solution, 
and  leave  it  in  that  condition  until  morning,  taking  care  that  the 
valves  do  not  leak,  that  the  iron  is  completely  covered,  and  that 
the  water  is  not  left  running,  as  iron  will  rust  in  running  water 
even  if  the  water  covers  it. 

In  rolling  a  batch  of  castings  it  will  often  be  found  that  a 
black  foam  will  rise  to  the  surface  of  the  solution  when  the  bar- 
rel is  opened  This  is  formed  by  the  iron  dust  left  on  castings 
that  are  cleaned  by  dry  tumbling,  and  it  will  also  be  found  when 


WATER  ROLLING,  TUMBLING  AND  SAND  BLASTING  57 

preparing  castings  that  have  been  faced  with  foundry  facing  of 
any  sort.  When  this  foam  or  scum  is  present,  let  water  flow  into 
the  barrel,  with  the  opening  in  a  position  that  will  allow  the 
objectionable  matter  to  float  off.  The  first  one  or  two  batches 
prepared  in  a  new  barrel  are  liable  to  give  trouble  in  tinning  unless 
the  inside  of  the  barrel,  with  the  shot  to  be  used,  is  cleaned  with 
a  strong  alkali  solution.  The  simplest  way  is  to  put  the  shot  into 
the  barrel,  and,  after  filling  it  about  half  full  of  strong,  hot  alkali 
solution,  close  the  barrel  and  allow  it  to  run  an  hour  or  more, 
after  which  the  interior  of  the  barrel  and  the  shot  used  should 
be  rinsed  with  plenty  of  clean  water. 

It  sometimes  happens  that  castings  are  encountered  which  have 
a  ground  work  of  delicate  design  into  which  the  sand  has  been 
burned.  If  such  castings  are  placed  in  the  rolling  barrel  with 
a  good  quantity  of  shot  and  given  two  or  three  hours'  rolling  in 
a  solution  of  hydrofluoric  acid  and  water,  1  part  acid  to  75  or  100 
of  water,  they  will  be  cleaned  very  nicely.  When  this  is  done  let 
the  hydrofluoric  solution  run  out  of  the  barrel  before  charging  it 
with  the  regular  solution  of  muriatic  acid,  sal  ammoniac  and 
water. 

The  operator  must  bear  in  mind  at  all  times  that  as  a  safe- 
guard against  accident  he  must  see  that  the  valves  on  the  rolling 
barrel  are  kept  in  good  working  order.  These  valves  should  be 
adjusted  to  open  at  a  pressure  of  4-0  pounds.  If,  by  reason  of  a 
leak  in  any  part  of  the  barrel,  gas  is  not  generated  the  work 
will  not  tin  properly.  Do  not  approach  the  barrel  with  a  light 
at  any  time  when  the  gas  is  escaping,  or  at  any  time  when  the 
gas  is  being  generated  in  the  barrel.  If  after  stopping  the  barrel 
it  is  found  that  the  valves  leak,  as  they  may  from  becoming  clogged, 
stop  the  leak,  as  the  solution  will  escape,  thereby  allowing  the 
work  to  oxidize.  Badly  oxidized  castings  will  not  tin.  The  solu- 
tion contained  in  tank  F,  Fig.  51,  is  calculated  to  remove  a  light 
oxide,  but  castings  that  are  heavily  oxidized  must  be  re-rolled. 

Storing  the  Castings  After  Tumbling 

As  soon  as  the  operator  has  determined  that  the  castings  are 
properly  rolled  for  tinning  he  proceeds  to  dump  the  contents  of 
the  tumbling  barrel  into  the  receiving  tank,  located  directly  under 
the  barrel.  The  cubic  contents  of  this  tank  should  be  about  one- 
third  greater  than  the  rolling  barrel.  From  this  receiving  tank 


58  GALVANIZING  AND  TINNING 

the  castings  should  he  removed  to  the  storage  tank  designated 
C  in  Fig.  51.  A  good-sized  coke  fork  is  best  for  handling  the 
castings  from  tank  to  tank,  as  it  lets  the  shot  or  stars  fall  to  the 
floor  separate  from  the  castings. 

In  placing  the  castings  in  the  storage  tank  care  should  be 
taken  to  have  those  with  depressions  or  cavities  go  under  the  water 
with  the  openings  up.  In  other  words,  castings  of  a  shape  that 
would  retain  pockets  of  air  under  the  water  should  be  so  placed 
that  no  air  can  be  retained.  If  air  is  retained  there  will  be  a 
rusty  place  formed  on  the  casting  to  which  the  tin  will  not  adhere. 
The  water  in  storage  tank  C,  Fig.  51,  will  in  a  short  time  become 
charged  with  the  acid  solution  from  the  rolling  barrel  unless  it 
is  changed  frequently.  If  much  acid  is  present  in  the  water  it 
will  impair  the  action  of  the  alkali  solution  into  which  the  cast- 
ings pass  directly  from  this  tank.  If  a  few  pounds  of  the  alkali 
selected  for  use  (caustic  soda  or  soda  ash)  is  added  two  or  three 
times  a  week  to  the  alkali  solution,  it  will  do  its  work  properly 
for  some  time,  although  it  is  best  to  clean  out  the  tank  and  make 
up  fresh  solution  once  in  two  weeks  when  it  is  in  constant  use. 

Cleaning  Work  with  the  Sand  Blast 

While  the  art  of  sand  blasting  is  old,  its  use  in  preparing  mate- 
rial to  be  galvanized  or  tinned  is  comparatively  new. 

Not  so  many  years  ago  the  process  of  tinning  common  gray 
iron  was  considered  a  great  secret.  As  a  matter  of  fact,  there  were 
only  one  or  two  concerns  able  to  do  it  on  a  commercial  basis,  and 
their  operation  was  confined  to  comparatively  small  castings.  The 
methods  employed  were  complicated  and  expensive.  The  use  of 
the  sand  blast  has  made  the  tinning  of  gray  iron  a  simple  matter, 
especially  in  the  case  of  unusually  large  or  fragile  castings. 

While  the  best  commercial  appearance  is  still  obtained  by  use 
of  the  wet  rolling  barrel,  there  are  many  kinds  of  castings  that  it 
is  impracticable  to  prepare  in  that  manner  owing  to  their  size  or 
delicate  construction.  To  obtain  even  fairly  economical  time  re- 
sults with  the  water  rolling  barrel  it  is  necessary  to  have  it  re- 
volve not  less  than  35  or  40  revolutions  per  minute,  and  even  with 
this  speed  it  takes  no  less  than  3  hours  to  properly  prepare  a  batcli 
of  castings  for  tinning,  and  often  a  much  longer  time.  On  the 
other  hand,  the  sand  blast  barrel  will  prepare  a  similar  batch  of 
castings  in  from  15  to  20  minutes. 


WATER  ROLLING,  TUMBLING  AND  SAND  BLASTING 


Cold  galvanizing  as  well  as  Sherardizing  can  be  done  on  work 
coming  direct  from  the  sand  blast,  practically  eliminating  the  use 
of  acids,  and  a  much  brighter  coating  is  obtained.  As  acid  works 
more  or  less  into  castings  in  the  cleaning  process,  even  its  partial 
elimination  is  another  distinct  feature  in  favor  of  sand  blasting 
for  any  process  of  coating. 

Another  feature  in  favor  of  the  sand  blast  is  that  old  work  can  be 
thoroughly  and  quickly  cleaned  by  this  method.  It  is  our  prac- 
tice to  use  a  pressure  type  of  hose  machine  in  the  cleaning,  for  hot 
galvanizing  of  old  anchors,  old  anchor  chain,  and  in  fact  old 
material  of  a  heavy  nature  of  almost  every  kind. 


FIG.  31 — A  SIMPLE  TWO-HOSE  TYPE  OF  SAND  BLAST 

The  large  variety  of  shapes  and  weights  of  castings  makes  it 
impossible  for  us  to  give  a  definite  time  for  cleaning  by  this 
method.  In  a  general  way  we  will  say  that  such  articles  as  food 
choppers,  saddlery  hardware,  etc.,  when  cleaned  in  a  sand  blast 
barrel  will  require  from  10  to  15  minutes,  the  consumption  of 
free  air  per  minute  being  135  cubic  feet  at  60  pounds  pressure, 
while  heavier  castings  or  old  work  that  is  badly  rusted  may  re- 
quire a  considerably  longer  time.  For  steel  castings  and  forgings 
a  higher  pressure  will  give  the  best  results.  This  applies  to  both 
the  hose  and  the  automatic  machine  type. 

The  value  of  the  sand  blast  for  plating  plants  in  general  is  only 
beginning  to  be  appreciated,  and  while  it  does  not  entirely  elimi- 
nate the  use  of  acids,  it  goes  a  long  ways  in  that  direction  and  is 
one  means  of  making  working  conditions  in  a  hot  galvanizing 
plant,  which  are  bad  enough  at  best,  much  more  endurable. 

That  the  subject  of  sand  blasting  and  the  apparatus  referred 


GALVANIZING  AND  TINNING 


to  may  be  better  understood,  we  refer  to  the  same  herewith  more 
fully.  The  term  sand  blast  in  its  simplest  form  means  a  stream 
of  sand  and  air  under  pressure.  In  this  condition  the  sand  gather- 
ing velocity  as  it  is  carried  along  with  the  air  strikes  the  object  in 
its  path  with  great  force.  The  cutting  action  of  the  blast  is  greater 
when  the  blow  is  slantwise  rather  than  straight  against  the  object. 
A  simple  form  of  sand  blast  de- 
vice can  be  made  from  a  Y  pipe  fit- 
ting, using  regular  stock  fittings  to 
complete  the  job,  but  the  action  of 
the  blast  would  destroy  the  several 
parts  after  a  few  hours'  service.  Far 
better  satisfaction  will  be  obtained  by 
purchasing  an  outfit  like  that  shown 
in  Fig.  31.  One  popular  and  service- 
able suction  sand  blast  outfit  consist- 
ing of  cast  iron  nozzle  with  remov- 
able air  tip,  easily  replaceable  hard 
iron  blast  tip,  air  valve,  sand  hose, 
sand  blast  helmet  and'  gloves,  costing 
not  over  $25.00.  In  this  type  of  ap- 
paratus the  end  of  the  sand  hose  is 
placed  in  a  pail  or  pile  of  sand  and 
the  air  turned  on  at  the  nozzle. 
The  next,  and  most  widely-known 
rstem,  is  the  pressure  or  single  hose 
type,  where  the  sand  is  placed  in  a 
closed  tank  and  air  admitted  to  the 
same  under  the  same  initial  pressure 

FIG.    32— SINGLE    HOSE    TYPE  as  that  to  be  used  in  the  blast.     In 

SAND  BLAST  APPARATUS         ,,  .  ,  .  .„  ,.        -n-      Oil 

this  machine,  see  illustration,  Fig.  32, 

there  is  a  mixing  chamber  at  the  bottom  into  which  the  sand  is  fed 
through  a  valve,  and  the  sand  mixing  with  the  air  which  is  ad- 
mitted through  a  separate  opening  is  discharged  through  a  single 
hose.  At  the  outer  end  of  the  hose  is  a  hard  iron  nozzle  holder, 
having  means  for  replacing  the  hard  iron  tip  which  wears  away 
very  rapidly.  The  hose 'must  be  specially  made  for  sand  blast  use, 
the  core  being  composed  of  practically  pure  rubber. 

The  present  tendency  in  sand  blast  practice  is  toward  higher 
air  pressures,  say  60  pounds,  using  smaller  nozzles  and  hose.  It  is 
easier  for  the  operator  to  handle  this  apparatus  than  the  more  cum- 


WATER  ROLLING,  TUMBLING  AND  SAND  BLASTING          61 

bersome  where  lower  pressures  are  used.  The  maintenance  cost  is 
also  less.  A  very  satisfactory  outfit  consists  of  tank,  one-inch 
hose  and  £-inch  blast  nozzle,  the  consumption  of  free  air  at  60 
pounds  pressure  being  about  6?  cubic  feet  and  the  power  required 
to  compress  the  air  approximately  10  H.  P. 

The  present  tendency  is  to  get  away  from  the  hand  operated 
blast  owing  to  the  reluctance  of  men  to  follow  this  work  continu- 
ously. Accordingly  self-contained,  dustless  machines  have  been 
designed  which  handle  tons  of  material  in  a  day.  These  are  made 
in  the  form  of  a  rotary  table,  a  sliding  table  or  planer  type  and 
revolving  barrel. 

Sand  Blast  Rolling  Barrel 

For  cleaning  small  and  medium-sized  castings,  forgings,  etc., 
the  sand  blast  rolling  process  is  to  be  preferred  in  many  ways.  A 
popular  type  is  shown  in  Fig.  33. 

The  self-contained  feature  confining  the  blasting  operation  and 
recovery  of  abrasive  to  the  inside  of  barrel  makes  it  a  dustless, 
as  well  as  a  more  efficient,  method. 

The  process  is  entirely  automatic  after  the  work  is  placed  in 
machine,  and  the  operator  is  at  liberty  to  attend  to  other  matters 
if  he  so  desires. 

Unlike  the  tumbling  mill  running  approximately  40  R.P.M., 
the  sand  blast  rolling  barrel  revolves  2  E.P.M.,  making  it  possible 
to  clean  fragile  castings  without-  rounding  the  corners,  etc. 

This  method  has  proven  valuable  in  cleaning  letters  or  orna- 
mental design  work  on  castings,  the  slow  movement  of  barrel  pre- 
vents defacement  and  the  blast  removes  all  dirt  and  cleans  them 
perfectly. 

The  inner  barrel  B  in  Figs.  34A  and  34s  is  made  from  heavy 
sheet  steel,  one-half  inch  thick,  having  a  number  of  holes  in  same 
which  allows  the  sand,  after  coming  from  the  blast  nozzle  F  and 
striking  castings,  to  fall  through  at  bottom  of  inner  barrel  B  to 
outer  shell  A.  As  the  barrel  revolves  (direction  of  arrow)  the  sand 
or  grit  falls  into  buckets  C  and  is  carried  to  the  top  of  the  barrel, 
where,  by  its  own  gravitation,  it  falls  back  through  the  holes  which 
it  entered,  passing  through  screen  E,  removing  all  foreign  sub- 
stances, into  sand-hopper  D,  ready  to  be  used  again. 

G  is  the  exhaust  pipe  for  removing  dust,  H  the  slide  valve  in 
hopper,  I  the  cast  steel  hopper  support,  J  the  petcock  for  drip, 
K  the  compressed  air  inlet,  L  the  exhaust  outlet. 


62  GALVANIZING  AND  TINNING 

While  it  is  possible  to  do  sand  blasting  in  an  open  space,  yet 
the  dust  arising  from  the  operation  is  so  objectionable  that  it  is 
customary  to  provide  a  room  for  this  work,  the  same  to  be  con- 
nected to  an  exhaust  fan  having  capacity  sufficient  to  change  the 
air  in  the  room  not  less  than  five  times  every  minute.  Fresh  air 


FIG.  33 — SELF-CONTAINED  SAND  BLAST  BARREL 

must  be  admitted  at  a  point  as  far  distant  from  the  exhaust  con- 
nection as  possible.  The  smaller  the  room  the  better,  for  less 
power  will  be  required  to  run  the  fan.  .The  walls  of  the  room 
are  usually  of  wood,  nailed  on  and  easily  renewed  as  occasion  de- 
mands. A  most  satisfactory  lining  is  discarded  fire  service  hose, 
which  should  be  split  and,  with  the  inner  side  facing  out,  nailed  to 
the  siding.  The  operator  must  be  provided  with  a  helmet  and 
should  also  use  a  respirator.  Leather  gloves  are  also  a  necessity. 


WATER  ROLLING,  TUMBLING  AND  SAND  BLASTING          63 


FIG.   34A — FRONT  VIEW,  SHOWING  DETAILS  OF  SAND  BLAST   BARREL 


m 


C^MJ  B*  \L\— 

h  l*LV:U?-~:~tevr^=^^s~=*^%v~^fe« 


FIG.  34e — SIDE  VIEW,  SHOWING  DETAILS  OF  SAND  BLAST  BARREL 


64  GALVANIZING  AND  TINNING 

It  is  always  important  to  use  a  good  hard,  washed  quality  of 
silica  sand,  passing  the  same  through  an  8  or  10  mesh  screen  for 
general  work.  The  sand  must  always  be  dry,  likewise  it  is  im- 
portant that  the  air  should  he  dry.  In  the  case  of  a  pressure  or 
closed  tank  system,  the  very  strictest  attention  must  be  paid  to 
these  particulars. 

Diamond  Grit  and  Steel  Shot  Used  as  Substitute  for  Sand 

In  many  instances  sand  is  being  replaced  by  steel  grit  or  chilled 
shot.  Both  have  their  particular  field,  the  shot  No.  5  Globe,  or 
16/30  Harrison,  giving  most  excellent  service  in  connection  with 
the  sand  blast  barrel.  As  this  class  of  material  is  expensive,  it 
must  not  be  allowed  to  go  to  waste,  good  floors  and  tight  rooms 
being  required  when  used  with  the  hose  machine. 

Diamond  grit  and  steel  shot  have  proven  a  very  satisfactory  sub- 
stitute for  sand,  though  opinions  differ  as  to  their  relative  value 
due  to  local  conditions. 

Diamond  grit  is  angular  in  shape  and  otherwise  known  as 
crushed  steel ;  its  edges  are  sharp  and  it  has  all  the  cutting  qual- 
ities of  sand. 

There  are  several  advantages  in  using  this  material  which  are 
due  to  its  slow  deterioration.  It  does  not  break  up  like  sand  and, 
therefore,  may  be  used  many  times  before  replacement  is  neces- 
sary. It  is  dustless  in  itself  and  naturally  eliminates  the  dust  that 
would  otherwise  be  generated  by  the  use  of  sand. 

This  material  is  made  in  a  number  of  sizes,  enabling  the  user 
to  adapt  a  size  satisfactory  to  the  finish  desired. 

Steel  shot  carries  the  same  general  advantages  as  grit,  though, 
being  globular  in  form,  its  actual  cutting  qualities  are  not  so 
severe.  Its  action  is  more  of  a  peaning  effect  rather  than  cutting, 
and  castings  cleaned  have  a  tendency  toward  a  shiny  appearance 
rather  than  the  sand  blast  finish  as  produced  by  sand  or  grit. 

Preparing  the   Cleaned   Work  for   Dipping 

To  enable  the  zinc  to  unite  with  the  work  properly,  a  solution 
of  muriatic  acid  and  water  is  used.  This  not  only  serves  as  a 
flux,  but  removes  any  rust  that  has  formed  on  the  work  in  the 
operation  of  inspection.  It  will  naturallv  be  inferred  from  the 
above  that  all  work  should  be  carefully  inspected  to  determine 
whether  the  cleaning  process  has  been  properly  performed  before 
it  is  subjected  to  the  muriatic  acid  treatment.  While  the  char- 


WATER  ROLLING,  TUMBLING  AND  SAND  BLASTING          65 

acter  of  this  muriatic  acid  dip  may  be  varied,  we  use  ordinarily  a 
solution  composed  of  one-half  acid  and  one-half  water,  liquid 
measure. 

Some  galvanizers  add  1  pound  of  sal  ammoniac  to  a  gallon  of 
the  mixture,  but,  in  inour  opinion,  the  advantage  gained  does  not 
warrant  the  expense.  Tank  C,  Fig.  3,  is  for  containing  this 
mixture. 

Drying  the  Work 

From  tank  C,  Fig.  3,  or,  in  other  words,  from  the  muriatic  acid, 
the  work  is  taken  to  the  place  provided  for  drying  it.  The 
position  of  this  drying  arrangement  is  designated  E  in  Fig.  3.  A 
drying  arrangement  for  a  limited  amount  of  work  may  be  the 
plates  covering  the  fires  that  heat  the  kettle.  If  the  work  to  be 
handled  only  amounts  to  a  few  hundred  pounds  per  day,  it  can  be 
dried  in  this  way.  If,  however,  the  amount  of  work  necessitates 
keeping  the  kettle  in  constant  operation,  a  drying  arrangement 
such  as  shown  in  Figs.  18  to  23  should  be  provided.  Sheets  and 
pipe  should  be  dried  in  an  oven. 

The  location  of  this  drying  arrangement  is  a  mere  matter  of 
choice.  In  Fig.  3  we  show  it  located  at  one  end  of  the  kettle. 
The  castings  or  other  work  to  be  dried  prior  to  galvanizing  are 
placed,  while  still  wet  with  muriatic  acid,  on  the  heavy  cast  iron 
top  plates  of  this  dryer  directly  over  the  fire  box,  where  they  are 
allowed  to  remain  until  thoroughly  dry,  when  they  should  be  passed 
to  the  end  of  the  dryer  farthest  from  the  fire  to  stay  until  needed. 
If  allowed  to  remain  on  the  hottest  part  of  the  plate  for  too  long 
a  time,  the  work  will  become  too  hot  and  the  acid  burned  off,  which 
will  necessitate  re-dipping  them  in  the  muriatic  acid  before  they 
can  be  galvanized  satisfactorily.  When  properly  dried,  the  salts 
formed  by  the  muriatic  acid  should  show  on  the  surface  of  the 
work  in  the  form  of  a  white  powder.  Work  that  has  been  prepared 
for  dipping  and  dried  should  not  be  allowed  to  get  cold ;  and  if 
more  material  has  been  prepared  for  dipping  than  can  be  finished, 
it  should  not  be  allowed  to  remain  on  the  dried  over  night,  but 
returned  to  the  water  tank.  It  should  be  remembered  that  rusting 
is  merely  oxidation;  and  freshly  cleaned  surfaces  readily  attract 
free  oxygen  from  the  air.  While  moisture  assists  rapid  oxidation, 
a  total  immersion  in  water  is  an  admirable  preventative  of  rust- 
ing. It  should,  of  course,  be  re-dipped  in  the  muriatic  solution  and 
dried  again  before  putting  it  into  the  galvanizing  kettle. 


CHAPTER  VH 

Hot  Process  of  Galvanizing 

Filling  a  New  Kettle 

WHEN  the  galvanizing  kettle  has  been  properly  bricked 
in  ready  for  use  considerable  care  must  be  exercised  in 
filling  it  with  spelter  to  prevent  the  kettle  from  being 
ruined  when  the  fires  are  started.  In  the  first  place,  a  suffi- 
cient quantity  of  lead  should  be  put  in  the  kettle  to  insure  a 
depth  of  not  less  than  6  inches  when  molten.  If  the  kettle  is  more 
than  30  inches  deep,  lead  should  be  introduced  to  insure  a 
depth  of  at  least  8  inches.  When  dross  forms  in  the  process  of 
galvanizing  this  lead  serves  as  a  "cushion"  for  it  to  rest  upon. 
Lead  and  spelter  do  not  mix  under  these  conditions,  the  lead  being 
of  a  greater  specific  gravity,  remains  at  the  bottom  of  the  kettle, 
and  no  amount  of  stirring  can  cause  any  considerable  quantity  to 
be  permanently  mixed  with  the  spelter.  As  a  matter  of  fact,  if 
lead  is  present  in  the  spelter  itself,  as  ft  sometimes  is,  most  of  it 
settles  to  the  bottom  of  the  kettle  when  the  spelter  becomes  melted. 
The  lead  not  only  serves  as  a  cushion  for  the  zinc  dross  to  rest 
upon  as  it  forms,  but  greatly  facilitates  the  removal  of  the  dross 
when  necessary.  It  is  also  a  protection  for  the  bottom  of  the  kettle 
and  keeps  the  spelter  and  dross  even  or  slightly  above  the  fire  line, 
as  it  should  be. 

In  filling  the  kettle  with  the  slabs  of  spelter,  place  them  on  edge 
in  sucli  a  way  that  their  flat  surface  will  lie  as  closely  as  possible 
to  the  sides  of  the  kettle.  By  exercising  a  little  ingenuity  the 
slabs  can  be  placed  so  as  to  practically  cover  the  sides  of  the  kettle. 
This  method  of  packing  the  slabs  will  materially  lessen  the  clanger 
of  burning  the  kettle  at  the  first  firing,  as  there  is  cold  zinc  against 
all  the  heated  surface.  These  slabs  should  also  be  so  arranged  that, 
as  the  outside  ones  melt,  those  next  to  them  will  be  forced  outward 
against  the  sides  of  the  kettle.  To  the  inexperienced  this  may 
seem  an  unimportant  matter,  but  we  can  assure  the  reader  that 
many  kettles  have  been  ruined  at  the  first  firing  through  failure 
to  give  proper  attention  to  these  details. 


HOT  PROCESS  OF  GALVANIZING  C7 

AVhen  a  galvanizing  plant  has  an  equipment  of  more  than  one 
kettle  it  is  a  good  plan  to  bail  molten  metal  from  a  kettle  already 
in  use  into  the  one  that  is  being  put  into  operation  for  the  first 
time,  after  the  slabs  have  been  properly  arranged,  and  before 
starting  the  fires.  Refill  the  kettle  in  operation  with  new  metal, 
replacing  what  has  thus  been  taken  out. 

Firing  a  New  Kettle 

In  heating  up  a  kettle  for  the  first  time  great  care  should  be 
exercised  that  the  work  is  not  hurried.  Under  no  circumstances 
attempt  to  melt  out  a  kettle  for  the  first  time  in  less  than  36 
hours.  Until  the  spelter  commences  to  melt  the  fuel  should  not 
be  allowed  to  attain  a  depth  of  more  than  12  or  15  inches  in  the 
fire  boxes,  and  the  slides  that  close  the  draft  holes  should  be  so 
regulated  that  the  fires  will  not  burn  too  strongly.  We  repeat 
that  plenty  of  time  should  be  taken  to  melt  the  metal  in  a  new 
kettle  the  first  time;  otherwise,  one  may  be  put  to  heavy  expense 
for  replacing  a  burned  out  kettle,  to  say  nothing  of  the  loss  result- 
ing from  over-heating  the  zinc.  As  the  metal  melts  the  depth  of 
fuel  may  be  increased,  but  it  should  never  be  more  than  3  or  4 
inches  above  the  molten  metal  in  the  kettle.  Of  course,  it  is  rather 
difficult  to  determine  just  the  depth  of  the  molten  metal,  but  it 
is  easy  to  be  on  the  safe  side  even  if  a  longer  time  is  taken  for  the 
"melting  out"  operation  than  is  actually  necessary. 

The  Temperature  of  the  Zinc 

The  question  of  the  temperature  of  the  zinc  is  the  most  difficult 
to  learn;  for  the  reason  that  different  kinds  of  work  demand  that 
different  temperatures  be  maintained.  A  kettle  of  zinc  at  the 
proper  heat  for  wire  or  wire  cloth  would  be  much  too  hot  for 
galvanizing  castings  of  either  gray  or  malleable  iron,  while  with 
the  metal  at  the  proper  heat  or  heavy  work,  it  would  be  impossible 
to  coat  small  work  properly,  even  if  the  material  was  the  same. 
Large  pieces  demand  that  the  galvanizing  bath  be  maintained  at 
a  low  temperature.  Small  work  that  is  strung  on  wires  for  dipping 
in  the  galvanizing  bath  demands  a  higher  heat  than  heavy  pieces. 
Work  that  is  galvanized  in  baskets  often  requires  a  still  higher 
heat  than  work  that  is  strung  on  wires,  as  hereafter  described. 

We  shall  give  the  degrees  of  heat  that  a  pyrometer  should  indi- 
cate when  different  kinds  of  work  are  being  done,  basing  the  rules 


68  GALVANIZING  AND  TINNING 

given  on  the  supposition  that  when  the  metal  is  barely  melted — 
that  is,  at  a  temperature  that  would  just  keep  it  in  a  liquid  state, 
the  pyrometer  indicates  750  degrees  of  heat.  We  shall  also  give 
the  best  rules  possible  for  determining  the  proper  temperature  by 
the  appearance  of  the  metal  and  by  other  signs. 

Large  gray  iron  castings  require  that  the  metal  be  at  the  lowest 
temperature  possible  and  still  have  it  liquid.  At  about  this  tem- 
perature it  will  be  silver  white  in  color,  will  burn  sal  ammoniac 
slowly  when  thrown  on  its  surface,  and  when  a  skimmer  is  passed 
over  its  surface  the  oxide  will  be  slow  in  appearing.  With  the 
metal  in  this  condition  the  pyrometer  should  indicate  about  800 
degrees  of  heat.  This  temperature  is  also  suitable  for  galvanizing 
very  thin  castings  that  are  intended  to  be  "spangled"  or  to  have  a 
crystallized  appearance — for  example,  sinks  and  like  work. 

For  work  that  is  drawn  through  the  clear  metal  the  pyrometer 
should  indicate  not  less  than  850  degrees.  At  this  temperature 
the  metal  should  have  a  slightly  bluish  cast,  burn  sal  ammoniac 
moderately  quick  and  show  the  oxide  in  a  few  seconds  after  the 
skimmer  has  been  passed  over  its  surface.  This  temperature  is 
about  right  for  galvanizing  wrought  iron  pipe,  the  cheaper  grades 
of  sheet  iron  and  goods  made  from  it,  such  as  coal  hods,  ash  cans 
and  chamber  pails.  Heavy  malleable  iron  castings  will  also  coat 
nicely  at  this  heat. 

For  small  work,  such  as  nails,  and  in  fact,  almost  any  work  that 
is  done  in  baskets  or  strung  on  wires  and  drawn  through  flux,  the 
pyrometer  should  indicate  not  less  than  900  and  not  more  than 
925  degrees  F.  The  metal  at  this  heat  should  burn  sal  ammoniac 
quickly  and  oxidize  quickly,  and  will  be  quite  blue  in  color.  This 
temperature  is  about  right  for  sheet  steel  and  articles  made  from 
it,  as  well  as  steel  pipe. 

We  wish  to  impress  upon  the  reader  that  these  rules  for  tem- 
perature are  based  on  the  supposition  that  the  galvanizing  bath  is 
composed  of  strictly  Prime  Western  Spelter  that  has  not  been 
subjected  to  overheating,  and  that  the  bath  is  practically  fresh  by 
reason  of  recent  starting  or  recent  dressing  and  re-filling  with 
new  metal.  If  "Remelt"  spelter  is  used  exclusively,  or  even  par- 
tially, the  proper  degrees  of  heat  can  only  be  determined  by  ob- 
servation and  experience.  Therefore,  we  repeat  that  no  hard  and 
fast  rules  for  operating  the  bath  exclusively  by  the  pyrometer  can 
be  given. 


HOT  PROCESS  OF  GALVANIZING  60 

Dipping  the  Work  in  the  Molten  Zinc 

We  will  describe  the  manner  of  handling  several  different  ar- 
ticles as  a  general  guide  for  dipping  all  kinds  of  work.  Consider- 
able skill  is  required  to  bring  work  out  of  the  molten  metal  and 
cool  it  in  such  a  manner  that  the  surface  will  be  smooth,  free  from 
blisters  and  without  lumps  of  surplus  metal  attached. 

Before  commencing  to  dip  the  work,  cover  part  of  the  surface 
of  the  molten  zinc  with  a  sal  ammoniac  flux  to  keep  the  oxidized 
metal  from  adhering  to  the  material.  To  prepare  this  flux,  sprinkle 
a  few  handfuls  of  sal  ammoniac  on  the  surface  of  the  bath,  and  as 
soon  as  it  is  melted  add  a  few  drops  of  glycerine.  This  will  cause 
the  flux  to  thicken  somewhat  and  will  prevent  it,  in  a  measure, 
from  covering  the  entire  surface  of  the  metal.  The  glycerine  also 
causes  the  flux  to  remain  stationary,  so  that  when  the  operator  is 
ready  to  draw  work  from  the  bath  the  flux  will  not  cover  the  space 
he  has  cleared  with  his  skimmer  for  so  doing.  The  tool  desig- 
nated E  in  Fig.  25  is  a  skimmer  used  for  clearing  the  surface  of 
the  metal  before  drawing  work  from  the  bath. 

The  flux  not  only  prevents  the  zinc  from  oxidizing,  but  also  as- 
sists the  metal  in  adhering  quickly  and  evenly  to  the  work.  Keep 
the  flux  fresh  by  adding  more  sal  ammoniac  from  time  to  time  as 
required. 

We  will  suppose  an  article  to  be  dipped  is  a  cast  iron  sink  or 
some  similar  thin  casting,  in  which  case  have  the  metal  at  the 
temperature  first  described  under  the  heading  "The  Temperature 
of  the  Zinc."  After  satisfying  himself  that  the  casting  has  been 
heated  until  it  is  perfectly  dry,  the  operator  catches  the  article 
with  a  pair  of  tongs  and  plunges  or  drops  it  as  quickly  as  possible, 
without  causing  the  metal  to  spatter,  through  the  flux  into  the 
molten  zinc.  He  must  keep  the  article  beneath  the  surface  until 
it  becomes  as  hot  as  the  zinc  itself.  After  the  article  has  been  in 
the  bath  a  few  minutes  it  should  be  rinsed  or  washed  around  in 
the  metal  in  such  a  way  that  the  flux  will  come  in  contact  with  all 
parts  of  it.  When  the  article  is  thoroughly  coated  clear  a  space  on 
the  surface  of  the  molten  zinc  with  the  skimmer,  sprinkle  on  a  little 
dry  white  sal  ammoniac,  and  draw  the  article  slowly  from  the 
metal. 

In  performing  this  operation  catch  the  article  with  the  tongs 
in  such  a  way  that  the  part  they  grasp  will  be  the  last  to  leave 


70  GALVANIZING  AND  TINNING 

the  zinc.  Do  not  lift  the  article  clear  of  the  metal  with  the 
tongs  you  use  in  the  bath,  but  provide  a  second  pair  to  complete 
its  removal  and  to  handle  it  until  cooled.  Hold  the  article  in  such 
a  position  as  to  cause  the  surplus  metal  to  flow  to  one  point,  and 
just  as  the  drop  starts  to  harden  remove  it  with  a  stiff  brush  or 
an  old  file.  Expose  the  article  to  the  air  until  crystals  appear, 
and  then  brush  it  lightly  with  a  brush  wet  in  clear  water.  Do  not 
dip  the  article  in  water,  especially  if  it  is  a  very  thin  casting,  as 
that  would  be  quite  likely  to  break  it,  and  the  coating  would  not 
be  as  bright  as  if  left  to  cool  gradually  after  brushing  with  the 
wet  brush.  Thick,  heavy  castings  may  be  dipped  in  water  at  once 
on  removing  them  from  the  molten  metal. 

Coal  hods  and  similar  goods  of  sheet  steel  or  iron  only  need  be 
left  in  the  bath  a  few  seconds.  The  flux  through  which  they  pass 
should  be  confined  at  one  end  of  the  kettle  by  a  piece  of  sheet  iron 
long  enough  to  go  across  the  kettle  from  side  to  side.  This  is  called 
a  "flux  guard,"  and  it  should  enter  the  metal  about  2  inches,  with 
the  upper  edge  as  high  or  a  little  higher  than  the  sides  of  the 
kettle.  In  galvanizing  sheet  metal  ware  the  flux  should  be  made  to 
foam  up  nearly  to  |he  top  of  the  kettle  by. using  glycerine.  The 
goods  should  be  passed  through  the  flux  under  the  guard  to  the 
end  of  the  kettle  that  is  kept  clean.  In  passing  the  article  under 
the  flux  guard,  keep  the  opening  up  so  that  none  of  the  flux  will 
be  carried  along  with  it.  Remove  the  article  from  the  metal  in  the 
way  described  for  sinks  and  similar  articles,  but  do  not  sprinkle  the 
clear  surface  of  the  zinc  with  sal  ammoniac.  Allow  the  work  to 
cool  in  the  air.  If  any  particles  of  flux  have  adhered  to  the  work 
while  drawing  it  from  the  molten  metal,  remove  them  with  a  wet 
brush  while  the  article  is  still  hot. 

Some  articles  can  be  galvanized  to  best  advantage  by  stringing 
them  on  stout  wires  about  2  feet  long.  When  this  method  is  em- 
ployed, string  on  a  number  of  the  pieces  and  then  bring  both  ends 
of  the  wire  together  and  clinch  them  securely.  For  suspending 
work  in  the  metal  which  is  strung  this  way,  use  a  hook,  shaped  in 
the  form  shown  by  Fig.  25  and  designated  G.  Provide  several  of 
these  hooks,  so  that  a  batch  may  always  be  ready  for  removal  from 
the  kettle  when  the  previous  one  has  been  removed.  A  piece  of 
f-inch  round  iron,  bent  in  the  shape  of  the  letter  S,  may  be  used 
to  remove  the  strings  of  castings  from  the  hooks,  and  also  foi 
handling  them  until  they  are  cooled.  The  wires  C  and  D,  Fig.  25, 


HOT  PROCESS  OF  GALVANIZING  71 

are  also  intended  for  stringing  small  articles  for  the  purpose  of 
dipping  them  in  the  molten  metal. 

In  handling  small  articles  on  any  of  these  wires  after  they  are 
drawn  from  the  metal,  use  a  shaking  motion  that  will  free  them  of 
surplus  metal,  and  also  prevent  their  sticking  to  each  other  when 
plunged  in  the  water.  Some  practice  will  be  necessary  before  this 
can  be  done  properly. 

It  is  a  good  plan  to  warm  the  cooling  water  slightly  for  cooling 
some  articles,  arid  to  have  a  thin  film  of  oil  on  the  surface.  Small 
articles  strung  on  wires  may  be  drawn  from  the  clear  metal  after 
sprinkling  on  a  small  quantity  of  powdered  sal  ammoniac,  or  may 
be  drawn  through  a  clean,  thin  flux  of  sal  ammoniac,  to  which  a 
few  extra  drops  of  glycerine  have  been  added.  If  the  latter  method 
is  used,  as  it  should  be  if  the  articles  are  such  as  are  liable  to  rub 
and  stick  together,  oil  should  not  be  used  on  the  cooling  water. 

Small  work  that  cannot  be  strung  on  wires  may  be  galvanized  in 
a  wire  or  sheet  iron  basket.  We  have  already  described  these,  and 
they  are  designated  in  Fig.  25  as  A  and  B. 

When  baskets  are  employed,  the  flux  should  be  of  such  con- 
sistency that  it  will  flow  freely  among  the  work.  A  block  of  iron 
should  be  placed  on  the  brickwork  beside  the  kettle  in  such  a 
position  that  the  operator  can  rest  the  handle  of  his  basket  across 
the  block  with  the  basket  hanging  over  the  kettle.  Using  this  block 
as  a  rest,  the  operator  should  shake  the  basket  up  and  down  sharply 
for  several  seconds  vifter  it  has  been  drawn  from  the  bath  to  free 
the  work  of  surplus  metal,  and  when  this  is  accomplished  he  should 
dump  them  into  the  water  to  cool,  after  which,  dry  them  off  by  dip- 
ping in  boiling  water  and  throwing  them  into  dry  sawdust.  Nails 
or  tacks  may  be  shaken  out  of  the  basket  onto  an  iron  plate,  placed 
at  an  angle,  over  a  tub  of  water  to  separate  them.  The  plate 
should  be  inclined  sufficiently  for  the  work  to  slide  into  the  water 
readily. 

Considerable  difficulty  is  experienced  in  removing  the  surplus 
zinc  from  small  articles,  such  as  nails,  tacks,  bolts,  nuts,  washers, 
rivets,  screw  eyes,  screws  and  sheet  metal  or  wire  specialties  when 
hot  galvanizing  them  unless  mechanical  means  for  accomplishing 
this  purpose  can  be  employed.  This  fact  has  been  responsible  for 
the  invention  of  several  different  machines  and  devices  intended 
to  remove  the  surplus  metal  after  the  articles  have  been  taken 
from  the  molten  zinc.  Notable  among  these  is  the  "Porter  Ma- 


72  GALVANIZING  AND  TINNING 

chine/'  which,  according  to  the  inventor,  will  handle  anything 
from  a  small  tack  to  a  60-penny  nail  at  the  rate  of  from  2000  to 
3000  pounds  per  hour.  This  machine  removes  all  unnecessary 
surplus  metal  by  means  of  beaters  or  fans,  cools  the  articles  with- 
out their  coming  into  contact  with  water,  and  automatically  de- 
livers them  into  kegs  or  boxes  ready  for  shipment.  As  this  ma- 
chine occupies  considerable  space  and  has  a  large  capacity  it  is 
best  adapted  to  the  large  producer  and  has  been  used  by  such  con- 
cerns for  some  time  past.  Another  means  of  accomplishing  the 
same  result  is  found  in  the  "Watrous  Machine,"  which  utilizes  the 
action  of  centrifugal  force  for  throwing  off  the  surplus  metal  while 
it  is  still  molten.  This  machine  is  claimed  by  the  inventor  to 
have  been  in  successful  operation  for  some  time  by  several  manu- 
facturers. 

Various  other  machines  designed  for  the  same  purpose  are 
claimed  by  their  enthusiastic  inventors  to  attain  remarkable  re-% 
suits,  but  the  prospective  purchaser  of  any  such  device  or  machine 
should  -thoroughly  investigate  the  matter  before  making  a  decision, 
as  any  of  them  may  have  limitations  or  objectionable  features  which 
can  best  be  learned  from  some  one  other  than  the  inventor  who  has 
had  actual  experience  with  the  device.  Eemoving  surplus  zinc  is 
not  always  the  only  consideration  when  galvanizing  small  articles, 
though  many  inventors  seem  to  lose  sight  of  the  fact.  For  this 
reason,  the  cost  of  production  (when  considering  the  merits  of  a 
machine  or  process)  should  always  be  given  considerable  attention, 
and  cost  figures,  obtained  under  actual  working  conditions  and  not 
made  in  round  figures  from  estimates  or  unconfirmed  reports, 
should  be  secured  for  careful  consideration. 


CHAPTER  VIII 

Galvanizing-  Sheets 

SHEET  iron,  wire,  wire    cloth  and  poultry  netting  are  gal- 
vanized by  being  passed  through  the  zincing  bath  mechani- 
cally, and  as  the  mechanical  means  employed  are  so  varied 
and  complicated  we  shall  not  attempt  to  illustrate  them.     The 
galvanizing  of  these  materials  is  carried  on  principally  by  large 
manufacturers   who  produce   the  finished  article   from  the  raw 
material,   and   the  galvanizing  is  simply  one  process   of  manu- 
facture. 

As  a  brief  description  of  galvanizing  sheets  by  hand  may  be 
useful  to  some,  we  will  describe  the  old  hand  method  in  use  before 
the  introduction  of  mechanical  methods. 

The  hand  galvanizing  of  sheet  iron  requires  the  use  of  a  kettle 
long  enough  to  accommodate  the  sheet  and  deep  enough  to  permit 
of  its  being  dipped  in  the  bath  without  interfering  with  the  dross 
in  the  bottom  of  the  kettle :  consequently,  a  kettle  for  sheets  must 
of  necessity  be  not  less  than  8  feet  6  inches  long  by  4  feet  deep, 
and  it  should  not  be  less  than  18  inches  in  width,  and  a  better 
width  is  2  feet.  As  it  is  necessary  to  pass  the  sheet  into  the  molten 
metal  through  a  flux  of  sal  ammoniac  what  is  known  as  a  "flux 
guard"  is  employed.  This  flux  guard  should  be  made  of  T-iron, 
to  which  an  iron  plate  can  be  riveted  so  that  when  the  arrangement 
is  placed  in  the  bath  the  guard  effects  a  longitudinal  division  of 
the  metal.  This  flux  guard  should  be  wide  enough  to  go  under 
the  metal  2  or  3  inches  when  the  metal  is  at  its  lowest  working 
height.  After  a  sheet  has  become  thoroughly  coated  it  is  pushed 
to  the  side  of  the  kettle  that  has  not  been  covered  with  a  sal 
ammoniac  flux  and  withdrawn  from  the  metal  with  the  aid  of 
properly  shaped  tongs  attached  to  a  light  single  block  and  fall. 
If  the  pickling  and  inspection  of  the  sheet  has  been  properly  done 
the  coating  takes  place  without  the  usual  rinsing  or  washing 
through  the  sal  ammoniac  flux  floating  on  the  surface  of  the 
molten  bath;  but  unless  this  has  been  properly  done,  it  will  be 
necessary  to  wash  the  sheet  through  the  flux  until  a  perfect  coat- 
ing has  been  obtained. 

73 


74  GALVANIZING  AND  TINNING 

In  the  hand  dipping  method  of  galvanizing  sheets,  a  simple 
arrangement  was  used  that  permitted  the  operator  to  transfer  the 
sheet  from  the  side  of  the  kettle  where  it  entered  the  bath  to  the 
opposite  side  where  it  was  withdrawn,  and  also  permitted  the  edge 
of  the  sheet  being  lifted,  semi-automatically,  just  high  enough  out 
of  the  metal  to  permit  of  its  being  readily  seized  with  the  tongs 
used  for  withdrawing  it  from  the  bath.  It  was  the  practice  in 
some  plants  to  allow  the  coated  sheet  to  form  crystals  by  cooling 
in  the  air,  after  which  the  sheet  was  plunged  into  a  bath  of  cold 
water  and  dried  off  in  sawdust.  When  it  was  desired  to  have  a 
bright  plate  without  the  crystals  the  sheet  was  plunged  into  the 
water  immediately  after  it  had  been  drawn  from  the  molten  metal. 
This  prevented  the  formation  of  crystals  and,  as  stated,  produced 
what  was  known  as  bright  galvanized  sheets. 

Among  the  old  English  galvanizers  it  was  the  practice  to  carry 
a  clean  flux  of  sal  ammoniac  on  the  opposite  side  of  the  flux  guard 
from  which  the  sheet  entered.  This  prevented  oxidation  and  was 
the  means  of  producing  a  somewhat  thinner  coating.  It  was  also 
the  practice  of  some  operators  to  cover  the  metal  on  the  side  of 
the  flux  guard  from  which  the  sheet  was  drawn  with  foundry  sand 
or  coke  dust. 

Mr.  James  Davies,  an  English  authority  on  galvanizing  sheets, 
describes  in  his  book,  entitled  "Galvanized  Iron,  Its  Manufacture 
and  Uses,"  a  very  practicable  and  simple  mechanical  device  for 
the  galvanizing  of  sheets.  His  device  consists  of  a  strong  square 
iron  frame  in  which  two  rollers  work.  The  rolls  are  made  of 
hammered  forgings  and  turned.  He  gives  the  usual  size  as  3  feet 
6  inches  long  by  9  or  10  inches  diameter.  The  frame  and  rolls 
are  suspended  from  bars  placed  in  the  bath  at  such  a  depth  that 
the  rolls  are  completely  immersed  in  the  metal,  with  the  center  of 
the  rolls  from  14  to  15  inches  below  the  surface.  The  rolls  have 
a  hammered  wrought  iron  pinion  on  the  end  of  one  and  two 
wrought  iron  pinions  at  the  other  end,  and  are  driven  by  another 
wrought  iron  cog  wheel.  The  driving  shaft  should  have  a  four- 
cone  pulley  with  a  corresponding  cone  pulley  overhead  for  vary- 
ing the  speed  according  to  the  thickness  of  the  sheets,  as  a  thin 
sheet  takes  less  time  to  coat  than  a  thick  one.  With  this  arrange- 
ment what  is  known  as  a  flux  box  is  placed  on  the  entrance  side  of 
the  bath  and  one  on  the  exit  side  of  the  bath.  From  these  flux 
boxes  guides  are  arranged  which  are  removed  when  the  day's 


GALVANIZING  SHEETS  75 

work  is  finished.  The  sheet  goes  into  the  flux  box  in  the  wet 
state  and  as  it  emerges  from  the  flux  box  on  the  other  side  it  is 
seized  by  the  operator  with  a  pair  of  self-acting  tongs  which  are 
attached  to  a  rope  running  over  a  pulley.  The  action  of  the  rolls 
in  the  bath  keep  up  a  constant  circulation  of  the  metal,  which,  in 
a  measure,  prevents  the  dross  from  solidifying. 

In  addition  to  this  comparatively  simple  method  of  galvanizing 
sheets  automatically,  we  have  what  is  known  as  the  "Heathfield's 
Patent  Process,"  the  advantages  of  which  are  best  described  in  the 
patentee's  own  language,  which  is,  in  part,  as  follows: 

"One  man  and  one  boy  are  sufficient  to  run  the  machine,  and 
their  combined  labor  will  turn  out  far  more  galvanized  sheets  per 
day  than  a  much  larger  number  of  men  can  do  by  any  other 
process. 

"The  machine  will  turn  out  with  sufficient  labor  12  tons  or 
more  of  galvanized  sheets  assorted,  14  to  30  gauge  or  thinner,  per 
turn  of  10|  hours,  and  with  a  good  dipper  will  sometimes  do  as 
much  as  11  or  12  tons  per  turn  of  sheets  assorted  26  to  30  gauge; 
while  8  English  tons  is  a  very  moderate  average  in  a  turn  of  10£ 
hours  for  sheets  of  these  latter  thicknesses. 

"The  machine  will  do  any  thickness  from  14  to  30  gauge  or 
thinner,  any  width  up  to  4  feet  (or  wider  if  a  large  enough  ma- 
chine is  supplied)  and  any  required  length. 

"As  the  pot  is  only  2  feet  8  inches  deep,  and  holds  only  about 
12  tons  of  spelter  (zinc),  the  very  large  output,  compared  to  the 
quantity  of  spelter  in  a  molten  state,  reduces  the  dross  made  per 
ton  of  sheet  below  that  made  by  any  other  plan ;  the  pot,  of  course, 
being  pushed  to  its  maximum,  and  worked  night  and  day. 

"No  oxide  is  made  while  the  machine  is  at  work. 

"The  quantity  of  muriate  of  ammonia  used  per  ton  of  sheets  is 
very  small.  Fourteen  pounds,  or  less,  will  suffice  to  galvanize  one 
ton  of  sheets,  28  gauge  thick,  while  stronger  sheets  take  propor- 
tionately less. 

"The  coke  bill  is  small.  If  the  pot  is  kept  fully  at  work,  six 
tons  of  ordinary  gas  coke  of  fair  quality  will  keep  the  pot  at  work 
a  week,  including  firing  it  on  Sundays. 

"The  quantity  of  spelter  used  per  ton  of  galvanized  sheets  made 
is  greatly  reduced,  while  the  appearance  of  the  sheets  is  much  im- 
proved, and  they  leave  the  machine  ready  for  use,  without  any 
subsequent  brushing,  washing  or  drying. 


76  GALVANIZING  AND  TINNING 

"The  following  are  the  approximate  quantities  of  spelter  de- 
posited on  the  sheets,  in  the  manufacture  of  one  ton  of  galvanized 
iron  by  the  Heathfield  patent  machine;  the  various  gauges  being 
calculated  at  the  number  of  galvanized  sheets  per  ton,  which  it  is 
usual  to  supply  in  England: 

16         18         20         24         26         28         30    gauge 
120       140       195       245       325       350       420  pounds 

"In  the  very  light  gauges  it  is  possible  to  use  sheets  a  gauge 
stronger  than  can  be  used  in  the  ordinary  process,  and  yet  pro- 
duce the  same  number  of  galvanized  sheets  per  ton  as  is  customary 
by  the  old  plan. 

"This  saves  considerably  the  cost  of  black  sheets  on  28,  29  and 
30  gauge  galvanized." 

In  addition  to  the  Heathfield  process  we  have  the  Bayliss  patent 
process.  The  patentee  makes  the  following  claims  for  his  process : 

"The  patentee  claims  that  this  method  dispenses  with  a  con- 
siderable amount  of  manual  labor.  The  patentee  passes  the 
sheets,  after  being  pickled,  through  a  pair  of  cold  rolls  upon 
which  a  stream  of  water  is  continually  flowing.  The  object 
of  this  is  to  impart  a  fine  smooth  surface  to  the  sheets  which 
have  been  roughened  by  the  pickling  process.  From  the  cold 
rolls  the  sheet  passes  onwards  towards  the  bath  which  it  en- 
ters through  a  pair  of  rolls  fixed  on  the  brickwork  of  the  gal- 
vanizing bath.  It  then  passes  through  a  guide  fixed  below  the 
surface  of  the  metal,  and  finally  emerges  through  a  layer  of  sand 
on  the  surface.  The  sheet  is  then  seized  by  a  pair  of  rolls  having 
studs  inserted  at  intervals  which  meet  and  grip  the  sheet.  The 
sheet  then  passes  on  by  means  of  an  endless  chain  band  to  a  set  of 
revolving  brushes  which  brush  off  any  adhering  particles  of  sand/' 


CHAPTER  IX 

Galvanizing  Wire,  Netting  and  Tubes 

WIRE,  wire  cloth  and  poultry  netting  are  galvanized  prac- 
tically  automatically.      In    galvanizing   wire    cloth    and 
poultry  netting  it  is  necessary  to  divide  the  molten  metal 
longitudinally  with  a  flux  guard  of  the  character  described  for  gal- 
vanizing sheets.     The  side  of  the  bath  where  the  material  enters 
should  be  covered  with  a  heavy  flux  or  sal  ammoniac,  and  the  side 
where  it  leaves  the  metal  should  be  covered  with  coke  dust  to  a 


FIG.  35 — AUTOMATIC  WIRE  GALVANIZING  MACHINE 


depth  of  several  inches.  The  coke  dust  must  be  constantly  sprinkled 
with  water  while  the  material  is  passing  through  it.  The  best 
means  to  accomplish  this  is  to  have  a  perforated  water  pipe  of 
the  required  size  constantly  discharging  water  in  sufficient  quan- 
tities to  keep  the  coke  dust  on  the  surface  of  the  metal  well  moist- 
ened. The  operation  of  drawing  the  work  through  the  molten 
metal  is  performed  by  a  revolving  drum  so  constructed  as  to  per- 
mit of  the  ready  removal  of  the  roll  of  wire  cloth  or  poultry  net- 
ting after  it  is  galvanized.  Where  wire  is  being  galvanized,  several 
strands  are  passed  through  simultaneously,  and  the  speed  varies 
according  to  the  gauge  of  wire  being  handled. 

A  description  of  a  device  that  is  claimed  to  be  an  improvement 
77 


78  GALVANIZING  AND  TINNING 

for  galvanizing  wire  cloth  recently  appeared  in  The  Brass  World, 
as  follows,  and  it  is  illustrated  by  Fig.  35. 

An  Improvement  in  Galvanizing  Wire  Cloth 

"An  improvement  in  galvanizing  wire  cloth  has  been  patented 
by  George  M.  Wright.  The  cloth  is  drawn  from  a  reel  down 
through  the  bath  of  molten  zinc,  contained  in  an  iron  kettle.  At 
the  bottom  of  the  kettle  are  roller  guides,  as  shown  in  the  illustra- 
tion. The  cloth  then  passes  through  a  mass  of  charcoal  9.  At 
the  same  time  a  lateral  motion  is  given  the  cloth  by  a  device 
shown.  The  charcoal  removes  the  surplus  zinc  from  the  top  and 
sides  of  the  wires  of  the  cloth,  but  on  the  bottom  of  the  meshes  it 
fails  to  brush  it  off.  By  giving  the  cloth  a  lateral  motion,  however, 
this  surplus  zinc  on  the  bottom  of  the  mesh  wires  is  scraped  off." 

The  Influence  of  Galvanizing  on  the  Strength  of  Wire 

As  there  are  enormous  quantities  of  galvanized  wire  used,  the 
effect  of  hot  galvanizing  on  the  strength  of  wire  may  be  of  interest 
to  some,  and  we  cite  the  following  from  The  Iron  Age. 

"At  the  International  Congress  of  Metallurgy,  held  at  Dussel- 
dorf  recently,  Dr.  Heinrich  Winter  of  Bochum  read  an  elaborate 
paper  on  the  above  subject.  Particularly  in  mine  installations  is 
it  important  to  protect  the  hoisting  ropes  by  a  suitable  rustproof 
covering.  Coating  with  zinc  has  been  found  to  answer  the  pur- 
pose admirably,  for  the  protection  afforded  depends  upon  the  for- 
mation of  a  couplet  in  which  the  zinc  of  the  galvanized  iron  forms 
the  electro  positive  element  and  the  iron  the  electro  negative,  when 
the  material  is  immersed  in  water  or  other  fluids.  The  zinc  takes 
up  oxygen,  gradually  forming  a  zinc  oxide,  while  on  account  of 
the  evolution  of  hydrogen  the  iron  remains  inert  even  if  the  con- 
tinuity of  the  zinc  coating  is  slightly  broken. 

"In  the  process  of  hot  galvanizing  there  is  no  question,  how- 
ever, but  that  the  strength  and  particularly  the  resistance  to  bend- 
ing and  torsion  are  considerably  affected,  and  the  purpose  of  the 
paper  in  question  was  to  determine  the  degree  of  this  action.  Many 
theories  are  given  regarding  the  loss  of  tensile  strength.  Poor 
material  is  cited,  but  tests  have  shown  that  even  the  best  of  mate- 
rial suffers  loss.  Again,  the  steel  is  supposed  to  have  been  'over- 
drawn,' but  microscopic  tests  do  not  show  signs  of  this  in  mate- 
rials losing  28  per  cent,  of  resistance  to  torsion  effects.  Finally, 


GALVANIZING  WIRE,  NETTING  AND  TUBES  79 

irregularity  in  the  coating  of  zinc  is  supposed  to  change  the  re- 
sistance to  torsion,  by  obstructing  the  power  applied,  in  varying 
degree  in  the  test  piece.  This  also  will  not  explain  the  situation, 
for  many  wires  with  uneven  coats  of  zinc  showed  practically  no 
deterioration  in  this  regard. 

How  Tests  Were  Made 

"To  study  the  matter  carefully,  the  first  thing  was  to  note 
whatever  changes  might  be  produced  by  the  drawing  down  of  the 
billet  to  wire.  Twelve  test  pieces  were  therefore  cut  from  the 
material  from  the  original  billet  down  to  the  actual  wire,  pickled 
and  galvanized,  but  not  annealed.  These  sections  represented  the 
various  stages  through  which  the  material  went,  and  were  etched 
by  immersion  in  a  copper-ammonium-chloride  solution  (1:12) 
for  one  minute  each,  the  copper  deposited  being  carefully  wiped 
off  with  absorbent  cotton  while  under  water.  The  lighter  outer 
zone  as  distinguished  from  the  darker  inner  zone,  showing  segrega- 
tion, could  be  followed  plainly  through  the  whole  series  made  from 
this  billet.  Further  etching  with  an  alcoholic  solution  of  picric 
acid  (1:  25)  for  15  minutes  indicated  that  the  grain  of  the  inner 
higher  phosphorus  zone  was  larger  than  the  outer  one  with  lower 
phosphorus.  The  results  of  the  physical  tests  on  the  material 
showed  the  usual  phenomena,  an  increased  ultimate  strength,  with 
brittleness  to  a  point  to  almost  wipe  out  the  power  to  twist  it  in 
the  final  wire  before  further  heat  treatment. 

"In  order  to  not  disturb  the  zinc  layer  in  making  sections  for 
polishing,  the  wire  was  first  cleaned  carefully  with  alcohol  and 
ether,  placed  in  a  solution  of  copper  potassium  cyanide,  and  a  weak 
current  applied  to  coat  it  with  copper.  It  was  then  washed  with 
alcohol  and  ether,  and  finally  melted  into  Rose's  alloy,  which  on 
account  of  its  low  melting  point  gave  a  perfect  protection  for  the 
galvanizing  coat,  and  yet  did  not  alter  the  miscrostructure  of  the 
material.  Finishing  up  the  polished  sections  with  a  very  little 
rouge  on  parchment  paper  with  a  2  per  cent,  solution  of  ammonium 
nitrate  for  five  minutes,  thus  etching  them,  gave  excellent  results. 
AVith  125  diameters  enlargement  the  makeup  of  the  section  is 
plainly  shown.  A  dark  band  for  the  zinc,  light  for  copper  and 
black  for  the  Eose  metal,  with  lighter  color  for  the  steel.  A  sepa- 
rate band  may  be  distinguished  between  the  iron  and  the  zinc 
coat. 


80  GALVANIZING  AND  TINNING 

Absorbed  Hydrogen  Gas  Does  Damage 

"This  material,  it  should  be  remembered,  was  pickled  before 
galvanizing.  Hence  many  investigators  brought  back  the  brittle- 
ness  of  galvanized  steels  to  an  absorbed  hydrogen  from  the  acid 
bath.  This  absorbed  gas  can,  therefore,  do  considerable  damage. 
Further  investigations,  however,  have  shown  that  heating  the  steel 
up  to  250  degrees  F.  for  four  hours  removes  this  effect  entirely. 
Hence,  inasmuch  as  the  microscope  does  not  show  any  indications 
of  an  iron  hydroxide  either  there  remains  only  the  theory  that 
between  the  zinc  and -the  iron  there  is  a  layer  of  an  iron-zinc 
alloy,  formed  either  because  the  wire  was  left  in  the  zinc  bath  too 
long  in  contact  with  the  zinc,  or  that  the  bath  was  too  highly  over- 
heated. That  such  an  alloy  exists  is  well  known,  every  galvanizer 
being  worried  by  large  amounts  of  'dross,'  which  contains  3  to  5 
per  cent,  iron,  and  is  a  very  brittle  material.  On  the  other  hand, 
in  order  to  get  the  zinc  coat  to  stick  to  the  iron,  it  is  necessary 
that  such  an  alloy  be  made  with  the  iron,  the  composition  varying 
from  high  zinc  at  the  contact  to  no  zinc  a  little  distance  into  the 
iron,  as  was  clearly  shown  by  Sherard  Cowper-Coles. 

"A  study  of  the  structure  of  the  material  before  galvanizing 
shows  that  where  this  is  large  grained  and  easily  to  be  penetrated, 
much  zinc  gets  in.  Even  where  the  microscope  does  not  show  the 
layer  of  the  zinc-iron  alloy,  it  is  undoubtedly  there  as  a  very  fine 
one,  and  depending  upon  the  extent  of  this  layer  will  be  found 
the  phenomenon  of  loss  in  power  to  bend  and  twist  when  taken  in 
connection  with  the  change  in  structure  through  the  heat  treat- 
ment. It  is  well  known  that  with  soft  steels  the  elasticity  is 
changed  with  temperatures  as  low  as  750  degrees  F.,  but  it  also 
takes  some  time  to  do  this.  Hard  drawn  steel  would  consequently 
become  softer  by  remaining  in  the  bath  longer,  but  this  gain  will 
quickly  be  offset  by  the  formation  of  a  heavier  layer  of  iron-zinc 
alloy. 

"The  conclusion  of  the  paper  is  that  the  wire  industry  is  per- 
fectly capable  of  furnishing  galvanized  wire  which  has  not  suf- 
fered seriously  as  to  its  physical  properties,  this  being  a  question 
of  proper  practice  in  regard  to  removal  of  damage  done  by  pick- 
ling, and  proper  bath  temperature  and  time  of  the  wire  remaining 
in  it.  It  is,  therefore,  necessary  to  treat  the  wire  before  galvanizing 
to  remove  the  hydrogen  absorbed  and  to  regulate  the  temperature 
of  the  zinc  bath  between  close  limits.  The  latter  is  not  easy,  as 


GALVANIZING  WIRE,  NETTING  AND  TUBES  81 

there  are  difficulties  in  pyrometry  and  also  in  the  proper  firing 
where  many  wires  are  passed  through  constantly  with  consequent 
irregular  lowering  of  the  temperature." 

The  Automatic  Galvanizing  of  Tubes 

Iron  and  steel  pipe  and  tubes  are  hot  galvanized  in  large  quan- 
tities annually,  and  large  tube  manufacturers  have,  of  course, 
adopted  mechanical  means  as  far  as  possible  for  handling  their 
product  through  the  galvanizing  process.  Many  ingenious  de- 
vices have  been  invented  and  many  of  them  are  patented.  Such 
a  device  was  illustrated  and  described  in  The  Iron  Age  recently 
as  follows: 

"An  arrangement  that  has  been  in  successful  operation  for  the 
last  three  years  at  Laurahiitte,  Upper  Silesia,  for  the  hot  galvaniz- 
ing of  tubes,  is  described  by  Engineer  G.  Buchert  of  Laurahiitte. 
Fig.  36  shows  the  details.  The  tube  a  is  drawn  out  at  one  end  of 
the  zinc  bath  &  and  passed  through  the  arrangement  c  for  remov- 
ing the  excess  spelter  from  the  outside  and  smoothing  the  surface. 
It  is  gripped  in  tongs  attached  to  a  specially  built  transverse  piece 
and  by  means  of  the  two  endless  chains  d  is  carried  up  the  incline 
e  and  along  the  upper  track  /.  After  the  lower  end  of  the  tube 
1ms  passed  through  the  cleaning  arrangement  it  falls  on  the  clean- 
ing grate  g,  and  automatically  cleans  itself  by  striking  against  the 
bars  of  the  grate,  so  that  all  the  excess  spelter  on  the  inside  of  the 
tube  falls  down  and  collects  in  the  space  h  underneath  the  grate. 

"After  the  tube  has  reached  the  end  of  the  grate  it  comes  on 
to  the  inclined  bench  I.  The  position  of  this  bench  when  at  rest 
is  horizontal,  slightly  higher  than  the  water  bosh  m.  (See  end 
view.)  The  falling  of  the  bench  to  the  inclined  position  is  brought 
about  by  the  wire  cable  n.  This  is  fastened  to  the  traveling  piece  o, 
which  is  carried  along  the  upper  track  by  the  tongs  (holding  the 
tube)  to  the  automatic  release  p.  The  moment  the  tongs  are 
opened  the  bench  /  carrying  the  tube  takes  its  original  horizontal 
position.  By  means  of  levers,  the  bench  is  inclined  and  the  tube 
rolls  of  itself  into  the  water  bosh  m.  It  is  raised  from  here  by  the 
revolving  shaft  q  with  its  star-like  arms  r,  and  rolls  down  the 
skids  into  a  car,  properly  galvanized  and  cooled.  The  tongs  and 
cross  piece  fall  down  the  incline  s  on  a  traveling  belt  t,  and  are 
carried  back  to  the  starting  place,  where  a  new  tube  is  taken, 
gripped  and  started  on  its  way  by  hand. 


- 


GALVAXIZIXG  AXD  TIXSTS'G 


GALVANIZING  WIRE,  NETTING  AND  TUBES  83 

"As  compared  with  hand  galvanizing,  the  apparatus  has  shown  a 
saving  in  wages  of  33^  per  cent,  and  in  spelter  of  0.8  per  cent,  of 
the  total  weight  of  tubes  to  be  treated.  Under  German  conditions 
this  amounts  to  $1.48  per  metric  ton  of  finished  tubes.  A  special 
crane  for  holding  and  agitating  the  tubes  during  pickling  is  also 
briefly  described,  which  has  proved  very  successful." 


CHAPTER  X 

By-Products  of  the  Hot  Galvanizing  Process 

THREE  by-products  are  produced  in  the  process  of  hot  gal- 
vanizing. They  are  known  by  the  trade  terms  of  "Hard 
Zinc  Dross,"  "Sal  Ammoniac  Skimmings"  and  "Zinc 
Ashes,"  sometimes  called  "Dry  Zinc  Skimmings,"  and  a  brief  de- 
scription of  each  is  given  in  order. 

These  materials  are  bought  by  all  the  principal  scrap  metal  deal- 
ers, who,  as  a  rule,  can  be  depended  upon  for  fair  business  deal- 
ings. There  are  exceptions,  however,  and  for  this  reason  sellers 
should  never  dispose  of  galvanizing  by-products  by  sample  nor 
allow  the  word  sample,  or  reference  to  any  particular  grade  of 
quality,  to  be  used  in  the  terms  of  sale.  The  buyer  may  be  per- 
mitted to  take  samples  of  the  materials  from  the  bulk  as  he 
chooses,  but  only  at  his  own  risk.  Each  lot  should  be  sold  on  its 
merits  as  it  stands  without  any  representations  as  to  quality  and 
absolutely  without  recourse,  except  in  the  matter  of  weights,  which, 
of  course,  should  be  as  unquestionably  accurate  as  possible.  We 
have  learned  through  experience  that  failure  to  take  these  pre- 
cautions may  lead  to  a  great  deal  of  trouble  and  expense. 

Prices  vary  with  the  price  of  Prime  Western  Spelter,  and  the 
quotations  made  are  usually  based  on  the  price  of  this  metal,  and 
the  terms  of  payment  in  the  sale  of  these  materials  are  nearly 
always  cash. 

Workmen  cannot  be  too  careful  in  the  removal  of  by-products 
from  the,  galvanizing  bath,  as  every  pound  of  good  zinc  removed 
unnecessarily  represents  a  direct  loss,  and  it  is  a  fact  that  gal- 
vanizing employees  as  a  rule  are  inclined  to  be  careless  with  and 
slow  to  appreciate  the  value  of  materials  which  they  use.  By- 
products are  valuable,  and  should  be  treated  and  stored  accord- 
ingly. It  is  economy  to  place  a  thoroughly  competent  and  con- 
scientious man  in  charge  of  a  galvanizing  plant  even  at  what 
might  seem  a  high  price.  The  man  who  is  satisfied  with  the  small- 
est salary  is  not  necessarily  the  cheapest  man,  and  the  fact  should 
not  be  lost  sight  of  that  a  few  dollars  saved  on  the  pay-roll  may 

84 


BY-PRODUCTS  OF  THE  HOT  GALVANIZING  PROCESS       85 

easily  be  more  than  offset  by  losses  due  to  incompetency  and  waste- 
ful carelessness  of  a  foreman  or  those  working  under  him. 

The  question  often  arises  as  to  whether  it  is  advisable  for  the 
individual  galvanizer  to  attempt  the  recovery  of  his  own  by- 
products. The  reclaiming  and  utilization  of  these  so-called  waste 
products  has  received  the  attention  of  scientific  men  in  recent 
years,  and  as  previously  stated,  have,  through  scientific  investiga- 
tions and  experiments,  been  made  to  yield  high  values. 

Commercially  practical  methods  for  the  economical  treatment 
and  use  of  drosses  and  skimmings  on  a  large  scale  have  heen  de- 
veloped with  the  result  that  galvanizers  can  now  secure  high  prices 
for  materials  which  were  formerly  consigned  to  the  dump  as  waste 
products,  and  it  is  doubtful  if  they  can  realize  as  great  returns 
by  the  treatment  of  their  own  by-products  as  by  selling  them  at 
prevailing  prices  to  the  large  buyers  who  make  a  specialty  of 
handling  these  materials. 

Zinc  Dross 

Zinc  in  a  molten  state  will  alloy  with  iron  so  that  iron  sub- 
merged in  it  will  begin  to  dissolve  as  soon  as  it  becomes  as  hot  as 
the  zinc  bath.  The  addition  of  only  a  small  percentage  (as  little 
as  3  or  4%)  of  iron  to  the  bath  will  form  an  alloy  of  zinc  and 
iron  called  zinc  dross,  that  is  of  greater  specific  gravity  than  zinc 
itself. 

This  dross  in  galvanizing  is  formed  principally  by  the  con- 
tinued washing  away  of  the  articles  which  are  being  galvanized, 
although  a  considerable  amount  is  formed  by  the  action  of  the 
zinc  on  the  inside  of  the  kettle,  as  evidenced  by  the  gradual  eat- 
ing away  of  galvanizing  kettles  from  the  inside  until  they  are 
eaten  completely  through,  necessitating  the  installation  of  a  new 
kettle,  and  if  by  accident  or  design  the  kettle  is  run  at  a  high 
heat,  dross  will  form  very  fast.  As  the  dross  forms  it  settles  to 
the  bottom  of  the  kettle  and  becomes  hard.  When  the  accumula- 
tion has  reached  a  point  where  it  interferes  with  the  work  it  must 
be  remoA'ed.  This  is  easily  done  Avith  the  use  of  a  proper  tool  made 
for  that  purpose  and  called  a  dross  scoop.  The  handle  of  the 
scoop  should  be  about  twice  the  length  of  the  kettle  unless  the 
kettle  is  of  a  size  requiring  the  use  of  tackle  in  dressing  it.  The 
scoop  should  be  well  perforated  with  holes  not  less  than  V'  in 
diameter  to  allow  the  clear  metal  to  flow  back  into  the  kettle,  and 


86  GALVANIZING  AND  TINNING 

care  should  be  taken  to  keep  these  perforations  always  open  and 
unobstructed. 

Before  commencing  to  dross  the  kettle,  i.e.,  to  remove  the  dross, 
skim  all  the  flux  from  the  surface  of  the  metal  with  a  perforated 
skimmer,  and  if  it  is  in  good  condition  save  it  for  future  use.  If 
this  flux  is  broken  up  when  cold  and  placed  carefully  back  on  the 
surface  of  the  zinc  it  will  soon  melt  to  its  former  consistency.  A 
perforated  skimmer  for  removing  sal  ammoniac  flux  and  zinc  ashes 
is  shown  in  Fig.  25  and  is  designated  F. 

When  drossing  do  not  stir  or  roll  the  bath  unnecessarily  in  forc- 
ing the  scoop  into  the  hardened  mass.  Force  the  scoop  gently  into 
the  dross  and  when  satisfied  that  it  is  full  raise  it  out  of  the  metal 
by  resting  the  handle  on  the  end  of  the  kettle  to  get  a  leverage. 
Let  the  scoop  remain  supported  on  a  bar  over  the  kettle  until  all 
the  liquid  metal  has  drained  back.  Dross  hardens  very  rapidly 
when  exposed  to  the  air,  and  no  more  time  than  necessary  to  allow 
as  much  good  metal  as  possible  to  drip  back  into  the  kettle  should 
be  consumed  before  getting  the  dross  into  the  dross  pans.  If  the 
handle  of  the  scoop  is  jarred  by  blows  from  a  hammer  or  bar  of 
iron  more  of  the  clear  metal  will  separate  from  the  dross  than  if 
this  was  not  done,  and  the  mass  of  dross  will  also  drain  much 
more  freely  if  cut  down  through  several  times  with  a  flat  iron 
shovel.  As  soon  as  clear  metal  ceases  to  drip,  dump  the  dross 
while  still  in  a  semi-fluid  state  into  cast  iron  pans  or  molds  made 
for  the  purpose  and  about  2"  deep,  15"  long  and  9"  wide  inside. 
The  dross,  while  still  hot,  should  be  worked  or  molded  into  the 
pans  and  smoothed  off  on  top  with  a  shovel.  When  the  dross 
hardens  in  the  molds  dump  them  and  you  have  the  commercial 
Hard  3inc  Dross. 

If  there  should  be  a  large  amount  of  dross  in  the  kettle  at  a 
time  when  it  is  desired  to  allow  the  fires  to  go  completely  out  it 
should  be  removed.  If  allowed  to  cool  with  a  large  amount  of 
dross  lying  in  the  bottom  the  result  will  most  likely  be  a  burst 
kettle. 

The  loss  caused  by  the  formation  of  dross  is  quite  large  even 
with  an  experienced  man  in  charge  of  a  kettle,  but  the  amount 
of  dross  made  is  greatly  increased  by  failure  in  keeping  the  metal 
at  a  temperature  which  will  not  injure  it ;  also  by  allowing  work 
to  be  logt  in  the  kettle  or  by  immersing  work  in  the  bath  that  has 
not  been  properly  prepared. 


BY-PRODUCTS  OF  THE  HOT  GALVANIZING  PROCESS          87 
Running  Over  or  "Sweating"  Zinc  Dross 

We  are  often  asked  whether  it  will  pay  the  small  galvanizer  to 
try  to  recover  the  good  zinc  from  his  dross,  and  if  so,  how  best  to 
accomplish  the  desired  results.  It  formerly  was  the  practice  of 
most  concerns  doing  galvanizing  to  run  over,  or,  as  it  is  termed, 
"sweat"  their  dross,  but  conditions  which  formerly  made  this  profit- 
able have  changed  materially  in  the  last  few  years.  At  the  time 
of  the  first  issue  of  "Galvanizing  and  Tinning"  the  very  best  zinc 
dross  could  be  bought  at  from  25  to  35%  of  the  price  of  spelter. 
To-day  the  most  inferior  grades  readily  bring  from  50  to  60%,  and 
some  of  the  better  grades  as  high  as  80%  of  the  price  of  the  best 
quality  of  zinc. 


FIG.  37 — DROSS  SWEATING  FUKNACE 

Without  entering  into  any  further  discussion  regarding  the  ad- 
visability of  attempting  the  recovery  of  zinc  dross,  we  reproduce 
the  illustrations  of  apparatus  for  "sweating"  dross  that  appeared 
in  the  first  issue  of  "Galvanizing  and  Tinning."  In  Fig.  37  we 
give  a  perspective  view  of  the  kettle  and  brick  work.  Fig.  38  is 
a  top  view.  Fig.  39  is  a  vertical  section  of  Fig.  38  at  A  A,  and 
Fig.  40  is  a  horizontal  section  of  Fig.  39  at  the  grate  line  B  B. 
The  kettle  and  casting  details  for  bricking  in  are  shown  in  Fig.  41. 
This  arrangement  is  so  simple  that  we  do  not  think  it  necessary  to 
describe  it  in  detail. 


8g  GALVANIZING  AND  TINNING 

A  kettle  30"  in  diameter  and  20"  deep  will  answer  the  purpose 
very  well,  and  should  be  made  of  cast  iron,  with  bottom  about  1* 
thick. 


-A 


FIG.  38— PLAN  OF  FURNACE 


FIG.  39 — VERTICAL  SECTION  OF 
FURNACE  AT  A-A  FIG.  38 


Section  B-B 
FIG.  40 — PLAN  OF  FURNACE  AT  GRATE  LINE 

To  separate  the  good  metal  from  the  dross,  first  melt  up  about 
6  or  8  inches  of  lead  in  the  bottom  of  the  kettle  and  then  put  in 
the  dross.  Bring  the  dross  to  a  temperature  that  will  cause  it  to 
have  rather  a  dark  blue  color,  or  to  a  point  where  the  pyrometer 
will  register  about  1050  degrees.  When  this  is  accomplished  stir 
the  mass  with  a  long-handled  ladle  for  about  one-half  hour,  and 
then  allow  it  to  settle.  When  the  mass  has  settled  the  lead  will 


BY-PRODUCTS  OF  THE  HOT  GALVANIZING  PROCESS 


80 


be  at  the  bottom,  the  dross  will  lie  on  the  lead  and  the  clear  metal 
will  be  at  the  top,  where  it  can  be  bailed  out  into  pans.  The  stir- 
ring may  be  repeated  once  or  twice  after  each  bailing  operation. 
After  all  the  clear  metal  available  has  been  extracted,  remove  the 
dross  and  put  it  into  pans  or  molds  as  when  first  taken  from  the 
galvanizing  kettle. 


FIG.  41 — CASTINGS  FOR  DROSS  SWEATING  FURNACE 

Sal  Ammoniac  Skimmings 

This  is  the  trade  term  for  the  sal  ammoniac  flux  used  on  the 
top  of  the  galvanizing  kettle  when  its  usefulness  as  such  has 
passed.  The  thick  dirty  portion  of  the  flux  must  be  removed  from 
time  to  time  as  necessary  and  should  be  placed  in  sheet  iron  pans 
of  convenient  size  to  cool,  when  it  will  be  the  commercial  Sal 
Ammoniac  Skimmings,  and  should  be  stored  in  a  dry  place.  In 
a  plant  operated  for  small  castings,  forgings  and  similar  work  this 
skimming  is  usually  done  twice  daily,  once  the  first  thing  in  the 
morning  and  once  before  starting  in  the  afternoon. 

Too  much  care  cannot  be  used  in  skimming  the  spent  flux  from 
the  'galvanizing  bath,  as  a  considerable  amount  of  zinc  can  be 
carried  off  in  the  flux  by  carelessness  without  its  being  noticed  or 
suspected,  and  may  be  the  means  of  quite  a  loss.  A  perforated 
skimmer,  shown  in  Fig.  25  and  designated  F.  should  always  be 
used,  and  it  should  be  kept  clean.  The  perforations  should  be 
sufficiently  large  to  permit  free  exit  of  metal,  about  £"  diameter, 
and  the  handle  of  the  skimmer  should  be  tapped  on  the  edge  of  the 


90  GALVANIZING  AND  TINNING 

kettle  while  filled  with  hot  flux  to  shake  out  as  much  of  the  free1 
metal  as  possible. 

Sal  Ammoniac  Skimmings  should  never  be  mixed  with  Zinc 
Ashes,  as  the  value  of  both  will  be  considerably  reduced  by  so 
doing.  Each  should  be  skimmed  from  the  bath  into  a  separate 
receptacle,  stored  separately  and  plainly  marked  when  packed  for 
shipment. 

While  several  methods  of  treatment  for  reclaiming  the  wastes 
of  Sal  Ammoniac  Skimmings  have  been  developed,  we  do  not  con- 
sider it  economical  for  the  individual  galvanizer  to  attempt  their 
recovery  on  a  necessarily  small  scale  for  reasons  previously  stated. 
In  a  plant  having  several  kettles  in  operation  considerable  zinc 
can  be  recovered  from  Sal  Ammoniac  Skimmings  with  little  ex- 
pense by  remelting  them  in  a  large  mass.  This  can  best  be  done 
after  drossing  when  the  surface  of  the  zinc  is  low  down  in  the 
kettle.  Put  several  days'  accumulation  of  skimmings,  which  have 
been  kept  in  a  dry  place,  into  the  kettle  at  once,  which,  when 
melted,  should  be  several  inches  deep  on  the  top  of  the  metal. 
Stir  this  mass  welt  with  a  poker  or  skimmer  and  then  skim  it  off 
into  flux  pans,  taking  first  the  lighter  top  portions,  and  being  care- 
ful to  dip  the  skimmer  through  into  the  molten  zinc  no  more  than 
necessary. 

Large  lots  of  Sal  Ammonic  Skimmings  are  often  shipped  loose 
in  bulk,  while  small  consignments  are  usually  forwarded  in  casks 
or  barrels. 

Zinc  Ashes 

The  name  Zinc  Ashes  is  the  trade  term  for  what  is  really  zinc 
oxide,  and  which  in  the  galvanizing  process  accumulates  on  the 
bare  surface  of  the  molten  zinc.  Zinc  Ashes  are  formed  by  con- 
tinually skimming  the  surface  of  the  bath  clean  for  the  withdrawal 
of  work  and  by  the  melting  up  of  new  spelter  after  drossing.  It 
also  collects  when  the  bath  is  lying  idle  if  it  is  in  a  molten  state, 
as  on  Sundays  and  holidays. 

Before  removing  Zinc  Ashes  from  the  kettle  a  little  white  sal 
ammoniac  should  be  sprinkled  over  and  well  stirred  into  them  with 
a  poker  or  skimmer.  This  will  be  found  of  great  assistance  in  re- 
ducing the  particles  of  metallic  zinc  to  a  molten  state. 

Plenty  of  time  and  care  should  be  used  in  skimming,  as  small 
drops  of  zinc  remaining  suspended  in  the  hot  ashes  are  very  hard 
to  shake  out,  and  carelessness  will  greatly  increase  the  losses. 


BY-PRODUCTS  OF  THE  HOT  GALVANIZING  PROCESS          91 

It  is  good  practice  to  screen  Zinc  Ashes  through  a  No.  6  or 
No.  8  mesh  riddle,  either  by  hand  or  machine,  before  packing  them 
for  the  market,  throwing  out  all  foreign  material.  A  surprising 
amount  of  zinc  can  be  recovered  in  this  way,  which  can  be  easily 
remelted  in  the  galvanizing  bath. 

Any  attempt  at  reclaiming  the  fine  ashes  does  not  pay,  as  the 
reduction  of  zinc  oxide  is  not  at  present  commercially  practical 
for  the  small  operator.  These  ashes  or  oxides  are  largely  used  by 
paint  manufacturers,  however,  and  they  find  a  ready  sale  in  the 
scrap  metal  market. 

Zinc  ashes  are  usually  packed  for  shipment  in  bags  or  barrels, 
and  should  always  be  stored  in  a  dry  place. 


CHAPTER  XI 

Replacing  Old  Galvanizing  Kettles 

GALVANIZING  kettles  are  good  for  service  until  they  begin 
to  leak  badly  or  have  become  so  warped  or  distorted  that 
they  cannot  be  operated  satisfactorily.  The  life  of  a  kettle 
ranges  from  a  few  days  or  weeks  to  several  years,  depending  on  the 
class  of  work  handled,  and  whether  it  has  had  careful  and  intelli- 
gent operation.  Comparatively  new  kettles  sometimes  develop  a 
leak  through  some  defect  in  the  steel  sheet  from  which  they  are 
made.  If  such  kettles  are  in  good  condition  otherwise  it  may  pay 
to  bail  the  molten  zinc  out  to  a  point  below  the  leak  and  repair 
it,  either  by  rivetting  on  a  patch  or  by  welding  with  electricity, 
oxy  acetylene  gas  or  other  method  that  seems  most  advisable  or 
economical. 

If  an  old  kettle  which  seems  to  be  generally  thin  and  worn 
starts  to  leak  it  is  usually  economy  to  tear  it  out  and  replace  at 
once  with  a  new  one.  If  a  successful  attempt  is  made  to  stop  a  leak 
in  an  old  kettle  of  this  kind  it  will  more  than  likely  start  to  leak  in 
other  places  within  a  very  short  time  and  your  trouble  and  ex- 
pense will  be  of  little  avail. 

When  a  kettle,  whether  old  or  new,  starts  to  leak  no  time  should 
be  lost  in.  bailing  the  molten  metal  out  to  a  point  below  the  leak, 
always  removing  as  much  dross  as  possible  before  taking  out  the 
clear  metal.  At  this  point'  it  can  be  decided  whether  or  not  to 
try  and  repair  the  kettle  and  if  not,  continue  the  bailing  operation 
until  "the  kettle  is  empty,  always  removing  the  dross  first.  When 
bailing  out  an  old  kettle  do  not  let  the  fires  cool  off  too  much, 
thereby  allowing  the  zinc  or  dross  to  congeal  on  the  sides,  as  you 
may  have  considerable  difficulty  in  removing  it. 

When  an  old  kettle,  especially  a  large  one,  suddenly  starts  to 
leak  badly  it  is  often  advisable  to  secure  considerable  extra  help 
in  order  to  remove  the  dross  and  metal  quickly,  thus  preventing 
the  molten  zinc  from  running  into  ash  pits  or  elsewhere  and  cool- 
ing in  such  a  way  that  it  cannot  be  easily  recovered  or  handled  for 
re-melting.  A  little  extra  expense  in  the  matter  of  labor  employed 
at  such  a  time  can  easily  result  in  a  substantial  saving  later  on. 

02 


REPLACING  OLD  GALVANIZING  KETTLES  93 

All  ordinary  iron  niolder's  ladle  with  an  iron  handle  makes  an 
excellent  tool  for  bailing  out  a  galvanizing  kettle,  and  several 
should  be  kept  on  hand  ready  for  use  it'  they  are  liable  to  be  re- 
quired in  such  an  emergency. 

After  an  old  kettle  has  been  bailed  out  as  clean  as  possible  draw 
the  fires  and  wet  it  down  with  water  to  hasten  the  cooling  off 
process  if  necessary,  after  which  remove  carefully  all  bolts,  nuts, 
castings  and  other  iron  work  for  use  again.  The  brick  work  can 
then  be  torn  down  to  the  foundation  and  the  old  kettle  removed, 
after  which  the  new  kettle  may  be  set  up  on  the  same  foundation, 
filled  with  zinc  and  heated  up  the  same  as  any  new  kettle,  instruc- 
tions for  which  are  given  on  pages  20  to  26  and  66  and  67. 


CHAPTER  XII 

The  Schoop  Metal  Spray  Process 

ONE  of  the  great  metallurgical  problems  of  the  day  has  been 
to  produce  a  non-corrosive  surface  on  iron  and  steel,  the 
indispensable  but  vulnerable  materials  of  engineering  con- 
struction, without  affecting  the  physical  properties  of  these  metals 
or  the  shape  or  usefulness  of  the  object  treated. 

There  are  demands  in  the  arts  for  a  method  which  will  take  the 
process  to  the  work  or  to  any  part  of  it,  and  will  secure  the  quick 
deposition  on  any  coherent  object,  whether  metallic  or  not,  of  any 
desired  metal  or  alloy  in  any  quantity,  however  minute. 

This  is  the  ideal  metal  coating  process.  Inventors  have  labored 
over  the  problem  for  many  years  but  commercial  results  have  not 
been  developed  until  recently  because  of  the  lack  of  economy  in 
the  earlier  forms  of  apparatus. 

The  overlaying  of  iron  and  steel  for  temporary  effect  with  non- 
metallic  substances,  such  as  paints,  enamel,  japan,  and  varnish,  has 
been  the  mechanical  method  necessarily  followed  hitherto  for  the 
great  bulk  of  metal  objects  and  structures  and  the  renewal  and 
maintenance  of  such  protections  involves  enormous  outlays.  It  is 
the  object  of  this  chapter  to  describe  the  latest  mechanical  process 
for  depositing  electro-positive  metals,  such  as  tin  and  zinc,  on  iron 
and  steel.  Incidentally,  the  method  permits  of  depositing  many 
other  metals  and  alloys  on  coherent  bodies  whether  metallic  or  not. 

The  Process  takes  its  name  from  M.  U.  Schoop,  an  engineer  of 
Zurich,  who,  in  collaboration  with  other  inventors,  made  the  metal 
spray  an  effective  coating  agent.  In  the  Schoop  Process,  the 
United  States  patents  for  which  have  just  been  issued,  the  coating 
metal  adheres  to  the  object  chiefly  by  mechanical  union.  The 
metal  is  discharged  in  hot  impalpable  particles  moving  with  high 
velocity,  and  these  when  directed  upon  a  prepared  object  penetrate 
the  pores  of  the  latter  while  the  spray  is  still  plastic.  The  coating 
metal  thus  dovetails  itself  into  the  superficial  pores  of  the  object 
and  does  so  in  the  presence  of  reducing  gas,  which  prevents  oxi- 
dation at  the  junction  of  the  metals. 

The  progress  of  invention  on  metal  spraying  has  been  chiefly 
94 


THE  SCHOOP  METAL  SPRAY  PROCESS  95 

directed  toward  making  the  metallic  particles  as  small  and  as  hot 
as  possible  and  to  avoiding  oxidation. 

In  1902  Thurston,  United  States  No.  706,701,  was  granted  a 
patent  for  impacting,  with  unignited  gas,  metal  in  the  form  of 
dust  upon  a  metallic  base.  His  apparatus  was  not  practical  and  no 
commercial  results  were  obtained. 

Within  the  past  year  four  United  States  patents  have  been  issued 
which  embrace  all  the  important  steps  since  Thurston's  invention. 

Schoop,  United  States  No.  1,128,058,  invented  a  process  for  pro- 
ducing a  fine  spray  from  either  molten  or  solid  metal  and  also  for 
producing  separable  metallic  coatings  or  copies  of  the  objects 
sprayed  upon ;  this  was  known  as  the  liquid  metal  spraying  process. 

Schoop,  United  States  No.  1,128,059,  later  invented  a  process  for 
projecting  finely  divided  unmolten  metal  particles  on  to  a  surface, 
using  an  ignited  gas  and  metal  in  the  form  of  dust  like  Thurston. 
This  was  known  as  the  metal  dust  spraying  process. 

Very  soon  afterward  Morf,  United  States  No.  1,128,175,  in- 
vented a  process  for  melting,  atomizing  and  projecting,  practically 
simultaneously,  solid  metal  and  particularly  metal  in  the  form  of 
wire.  This  was  known  as  the  metal  wire  spraying  process. 

At  the  same  time  Morf,  United  States  No.  1,100,602,  invented 
a  successful  apparatus  (known  as  a  "Pistol"),  for  effecting  this 
process. 

These  inventions  above  outlined  form  the  basis  of  the  Schoop 
Metal  Spray  Process  as  it  is  now  operated  in  the  United  States. 
The  present  chapter  is  wholly  concerned  with  the  apparatus  used 
for  tinning  and  galvanizing  by  this  method  and  with  the  applica- 
tions possible. 

The  evolution  of  the  apparatus  has  been  interesting.  The  liquid 
metal  process  involved  a  large  non-portable  reservoir  of  hot  metal 
weighing  with  the  auxiliary  parts  over  a  ton;  the  metal  dust  ap- 
paratus weighed  over  a  hundred  pounds,  while  the  "Pistol"  of 
to-day  weighs  less  than  four  pounds. 

Figures  A,  B,  and  C  show  the  three  forms  through  which  the 
apparatus  has  passed. 

In  the  apparatus  represented  by  Fig.  A,  a  melted  metal  is  allowed 
to  run  continuously  from  the  reservoir  "E"  through  a  broad  noz- 
zle "N,"  where  it  is  broken  up  and  swept  away  by  a  violent  cur- 
rent of  heated  gas  "G,"  issuing  under  regulated  pressure  from 
containers  "C"  and  reheated  in  its  passage  at  "H."  The  expansion 


06  GALVANIZING  AND  TINNING 

of  the  gas  chills  the  molten  particles  and  forms  a  rapidly  moving 
spray  or  fog  of  metal  which  impacts  upon  any  object  placed  in  its 
path  and  plates  it. 

Any  metal  fusible  under  the  conditions  of  the  apparatus  can  be 
used  and  owing  to  the  low  temperature  of  the  fog,  it  is  possible  to 
plate  very  delicate  or  easily  combustible  objects,  as  well  as  metal 
articles. 


FIG.  A — FIKST  TYPE  OF  METAL  SPRAY  APPARATUS 

Aluminum  plating,  which  could  not  be  obtained  by  fusion  or 
electrolysis  on  account  of  its  ready  oxidation,  was  easily  obtained 
by  the  Schoop  Process. 

The  obvious  objections  to  such  an  apparatus  were  lack  of  por- 
tability and  the  expense  of  melting  and  keeping  fluid  most  of  the 
metals  in  the  unavoidable  intervals  of  spraying.  The  result  was 
that  only  the  more  fusible  metals,  zinc  and  tin,  were  used  where 
spraying  on  a  continuous  scale  was  possible  and  the  liquid  metal 
apparatus  was  never  reduced  to  economical  practice.  It  was  ob- 
served with  this  apparatus,  however,  that  the  particles  were  not 
actually  molten  at  the  moment  of  impact  and  this  suggested  the 
next  step. 

Fig.  B  represents  the  second  form  of  apparatus  in  which  porta- 
bility was  secured  and  the  metal  particles  to  be  sprayed  were  pre- 
pared in  advance.  .  Powdered  metals  in  a  very  fine  state  of  division 
have  many  of  the  characteristics  of  a  liquid.  Their  fine  particles 
mix  with  one  another  like  drops,  they  spread  with  facility  and 
unite  under  the  influence  of  very  little  force. 

The  metal  powder  in  the  container  "C"  is  entrained  in  an  air 


THE  SCHOOP  METAL  SPRAY  PROCESS 


97 


a 


FIG.  B — SECOND  TYPE,  PORTABLE  METAL  SPRAY  APPARATUS 


ns 


GALVANIZING  AND  TINNING 


blast  "A,"  heated  in  the  flame  of  a  blast  pipe  "B"  and  projected 
with  high  velocity.  The  gas  is  burned  at  "A"  and  the  supply  of 
air  is  regulated  at  "S"  to  obtain  complete  combustion. 


FIG.  C — THIRD  TYPE  OR  METAL  SPRAY  PISTOL 

It  vas  found  that  the  anticipations  from  the  use  of  the  first 
apparatus  were  correct  and  that  metal  particles  projected  in  a 


FIG.  D— DETAIL  OF  METAL  SPRAY  PISTOL  NOZZLE 
pasty  condition  produced  plating  as  before.     Metal  powders,  how- 
ever, are  very  costly.     Most  of  them  tend  to  oxidize  rapidly  and 
the  use  of  this  apparatus  was  practically  restricted  to  zinc  on  that 


THE  SCHOOP  METAL  SPRAY  PROCESS  99 

account.  The  zinc  is  a  by-product  of  Zinc  Smelteries  and  is  readily 
applied  by  the  simple  apparatus  known  as  the  "Cyclone,"  which 
has  just  been  described.  It  is  still  the  most  economical  method  of 
producing  a  Schoop  coating  of  zinc. 

Inventors  set  themselves  to  overcome  both  the  chemical  and 

•Inner  Nozzle  that 
guides  wire 


Wire  of 
Coating 
Metar 


"CfTurbine 
Motor  that 
operates 
the  feed 


FIG.  E — SECTION  SHOWING  DETAIL  OF  CONSTRUCTION  OF  PISTOL 

economic  difficulties  with  other  metals  including  tin,  viz. :  to  dis- 
pense with  mass  melting  and  dust  preparation  and  to  secure  in- 
stant and  simultaneous  melting,  and  pulverization,  and  control 
with  a  handy,  economical  appliance.  The  result  was  the  ingenious 
instrument  known  as  the  "Pistol,"  which  is  shown  in  Fig.  C. 

The  principle  (Fig.  D)  consists  in  feeding  a  fine  wire  "W"  of 
any  metal  into  a  reducing  flame  zone  "Z"  at  such  a  constant  speed 
that  the  end  of  the  wire  "E"  remains  stationary,  its  melting  rate 
being  exactly  equal  to  the  rate  of  feed.  Under  such  conditions 
the  wire  end  melts  a  drop  at  a  time  and  each  drop  at  the  instant 
of  formation  is  struck  a  violent  blow  by  an  air  blast  "A." 

The  resulting  fog  or  spray  of  fine  particles  into  which  the  drops 


100  GALVANIZING  AND  TINNING 

are  divided  takes  the  form  of  a  diverging  cone  "C"  with  a  core 
of  reducing  gas  "G"  in  which  the  particles  are  entrained,  and  a 
surrounding  sheath  of  air  "A,"  which  is  rapidly  expanding  and 
cooling.  Any  suitably  prepared  object  placed  in  the  path  of  this 
metallic  spray  is  plated  through  impact  without  undue  elevation 
of  temperature. 

Fig.  E  is  a  section  of  the  commercial  spraying  pistol  now  in  use. 
The  principal  parts  of  the  pistol. consist  of  an  outer  casing  "A," 
cast  of  aluminum,  with  a  central  downward  projecting  tube  form- 
ing a  handle,  a  wire  feed  mechanism  mounted  entirely  upon  the 
cover  "B,"  of  the  turbine  chamber,  the  turbine  "C,"  actuating  the 
wire  feed  mechanism,  gas,  air  and  wire  nozzles  mounted  upon  the 
outer  casing  held  in  position  by  a  hand  nut  "D,"  and  a  removable 
cover  "F,"  which  completes  the  enclosure  of  the  outer  casing. 

Gas  and  air  ducts  are  drilled  in  the  outer  casing,  the  flow  con- 
trolled by  the  tapered  valve  "F"  provided  with  a  handle  "G." 

The  wire  feed  mechanism  is  actuated  by  a  turbine  "C"  mounted 
on  a  vertical  shaft  running  in  ball  bearings;  a  worm  is  cut  in  the 
upper  end  of  the  vertical  shaft  and  drives  by  worm  wheels  the 
horizontal  shafts  "N"  and  "0",  which  are  provided  with  worms  in 
turn  driving  the  worm  wheels  "P"  and  "Q." 

The  worms  "P"  and  "Q"  are  provided  with  slots  to  engage  the 
projecting  lugs  of  the  lower  feed  wheel  "E."  The  upper  feed 
wheel  "S"  mounted  in  the  pivoted  frame  "T"  is  provided  with 
shrouds  controlling  the  position  of  the  lower  feed  wheel  "E."  The 
lower  feed  wheel  can  be  engaged  in  either  work  "P"  or  "Q"  by 
raising  a  clip  "I"  shifting  laterally  in  either  direction  and  locked 
in  by  the  opposite  clip.  The  shift  can  be  readily  made  by  allowing 
the  mechanism  to  run  slowly  by  a  slight  opening  of  the  starting 
valve. 

Pressure  is  applied  to  the  feed  wheels  through  the  pivoted  frame 
"T"  by  a  coiled  spring,  and  controlled  by  the  operator  by  means  of 
the  release  lever  "K." 

The  final  adjustment  of  the  wire  feed  is  controlled  by  the  needle 
valve  "M."  The  turbine  and  shaft  complete  is  assembled  in  the 
outer  case  and  properly  adjusted  independently  of  other  mecha- 
nism. 

The  wire  feed  is  entirely  assembled  on  the  turbine  cover  "D" 
and  when  properly  adjusted,  secured  in  position.  The  wire  nozzle 


THE  SCHOOP  METAL  SPRAY  PROCESS  101 

base  "U"  provides  an  adjustment  for  position  of  wire  and  gas  noz- 
zles, and  is  secured  in  position  by  a  headless  set  screw. 

The  upper  end  of  the  stem  of  the  turbine  cover  is  provided  with 
an  annular  groove,  which  is  engaged  by  the  spring  loop  "V"  and 
secures  the  removable  cover  "E"  of  the  case.  Loop  "V"  provides 
a  means  for  hanging  the  pistol  on  a  conveniently  located  hook. 

The  Operation  of  the  Pistol 

The  gas  and  blast  nozzle  faces,  "B"  and  "C,"  are  securely 
clamped  to  form  gas  tight  joints  by  tightening  the  hand  nut  "D." 
The  end  of  the  central  or  wire  nozzle  is  then  .015"  inside  the  gas 
nozzle  and  the  stationary  melting  point  of  the  wire  is  .03"  inside 
the  air- blast  nozzle.  The  wire  diameter  used  is  from  .0319"  to 
.0375",  except  zinc  and  tin,  which  are  used  in  larger  sizes,  owing  to 
their  rapidity  of  melting. 

The  feed  gears  having  been  set  in  mesh  at  the  approximate  speed 
required  for  the  wire  selected,  the  air  alone  is  turned  on  and  the 
speed  tested  with  a  short  length  of  wire.  Adjustment,  if  neces- 
sary, is  made  by  the  needle  valve,  which  modifies  the  speed  two 
feet  per  minute  plus  or  minus. 

The  end  of  the  wire  reel  is  then  threaded  through  the  stock 
receiving  tube,  between  the  gripping  feed  rolls  and  into  the  cen- 
tral wire  nozzle  and  the  fuel  gas  pressures  from  the  containers  are 
adjusted  by  the  reducing  valves  and  gauges  thereon  to  the  tabular 
requirements  for  the  metal  to  l)e  sprayed.  The  pressures  of  the 
fuel  gases  seldom  rise  above  one  atmosphere  and  hydrogen  or  Blau 
gas  are  the  reducing  gases  usually  employed.  This  gas  is  now 
admitted  by  slightly  opening  the  starting  valve  and  when  ignited 
with  a  match  burns  quietly  as  a  pilot  light. 

The  starting  valve  is  then  opened  up  full  and  oxygen  is  admitted 
gradually  till  the  flame  zone  is  established.  All  back-firing  is 
avoided  by  keeping  the  reducing  gas  always  in  excess  of  the  oxy- 
gen, the  ratio  being  three  or  four  to  one.  The  above  movements 
are  made  in  rapid  succession  on  a  light  instrument  which  can  be 
held  in  one  hand  and  the  spray  is  started  up  the  moment  the  con- 
stant melting  position  of  the  wire  is  reached. 

The  spray  so  established  is  essentially  a  metal  plating  air- 
brush of  which  the  diameter  5"  from  the  pistol  end  is  about  2". 
Objects  to  be  plated  are  operated  upon  by  pointing  the  pistol  nor- 
mally to  the  surface  to  be  coated  at  any  moment  at  about  five  (5) 


102  GALVANIZING  AND  TINNING 

inches  distance  and  traversing  the  pistol  across  the  surface  with  a 
regular  motion. 

A  single  coating  is  about  .001"  thick.  The  operator's  vision 
easily  guides  him  in  distinguishing  between  the  coated  and  un- 
coated  portions  and  also  between  a  first  and  second  coat. 

Two  thousandths  of  an  inch  well  impacted  upon  a  surface  are 
just  as  effective  as  a  much  greater  thickness  and  of  course  unneces- 
sary sprayed  metal  increases  the  cost,  as  the  latter  is  directly  pro- 
portional to  the  thickness. 

Not  only  on  the  score  of  economy  but  also  to  preserve  tough- 
ness the  coating  should  be  of  minimum  thickness,  for  the  anvil 
action  of  the  metallic  spray  on  a  solid  metal  object  is  lost  above 
a  few  thousandths  of  an  inch  thickness  and  a  process  of  cold 
working  follows  which  produces  a  brittle  scale  readily  de- 
tachable. 

In  practice  this  matter  is  easily  regulated.  Pig.  C  shows 
the  pistol  held  in  the  hand  ready  for  action  with  the  wire  thread 
in  position.  Fig.  F  shows  the  pistol  applied  to  coat  a  wooden 
pattern  for  protection  with  tin.  Gas  bombs  with  fittings  and  air 
at  40  pounds  pressure  are  the  only  requisites  besides  the  "Pistol" 
and  its  hose  connections  for  plating  non-metallic  objects  such  as 
wood,  stone,  paper,  cement,  cloth,  etc.  All  metallic  surfaces  should 
have  the  scale  cleaned  off  and  their  pores  opened  by  preliminary 
sand-blasting. 

It  will  be  seen  from  the  tables  appended  that  .001"  thickness,  one 
square  foot  in  area,  of  the  common  metals  can  be  sprayed  for  a 
small  sum.  The  total  cost  is  five  cents  per  square  foot  for  tin  and 
two  cents  per  square  foot  for  zinc. 

Various  theories  have  been  offered  to  account  for  the  plating 
properties  of  the  Metal  Spray,  but  it  is  believed  by  those  putting  it 
to  practical  use  that,  except  in  the  few  cases  where  the  impacted 
metals  have  a  chemical  affinity,  the  action  of  the  spray  is  purely 
mechanical  and  restricted  to  superficial  pores  of  the  object. 

Metal  Spraying  is  essentially  a  kinetic  energy  process  and  the 
"Pistol"  is  practically  a  rapid  fire  gun  which  manufactures  its  own 
ammunition  automatically  from  a  reel  of  wire  and  discharges  an 
infinite  number  of  projectiles  which  impact  themselves  in  the  ex- 
posed pores  of  any  object  five  inches  away.  In  the  zinc  dust 
"Cyclone"  apparatus  the  size  of  the  projected  particle  is  predeter- 
mined, but  the  action  at  the  object  is  identical  with  that  of  the 


THE  SCHOOP  METAL  SPRAY  PROCESS 


103 


"Pistol."     In  either  case  with  proper  preparation  of  clean,  open 
surfaces  a  durable,  adherent,  protective  coating  is  attained. 

In  general,  the  applications  of  the  Metal  Spray  Process  may  be 
divided  into  five  groups,  namely,  protective  coatings;  bonding  or 


FIG.  F — METHOD  OF  USING  PISTOL  IN  SPBAYIXG 

junction  coatings;  electrical  coatings;  decorative  coatings;  and  de- 
tachable coatings  or  copies  of  the  objects. 

Protective  coatings  on  steel  or  iron  may  be  either  original  coat- 
ings of  the  whole  of  an  object  or  structure,  or  they  may  be  confined 
to  any  part  of  it,  or  they  may  be  merely  local  applications  with  the 


104  GALVANIZING  AND  TINNING 

"Pistol"  or  "Cyclone"'  apparatus  to  repair  damage  or  wear  to  a 
coating  of  tin  or  zinc  made  by  another  process.  The  repair  of  the 
troublesome  defects  found  on  many  galvanized  and  tinned  sheets, 
and  leading  to  their  rejection,  is  an  application  of  this  process 
which  is  made  only  through  the  possibility  of  applying  tin  or  zinc 
to  any  area,  however  small,  and  confining  it  to  that  area.  An- 
other application  for  the  same  cause  is  the  filling  up  of  pin  holes 
in  expensive  machine  castings,  such  as  printing  rolls,  etc.,  which 
would  otherwise  be  a  complete  loss. 

Many  engineering  structures  used  in  the  arts,  such  as  steel  and 
iron  tanks,  bridges,  girders,  and  machinery  of  all  descriptions,  cor- 
rode rapidly,  particularly  at  joints,  especially  if  exposed  to  atmos- 
phere or  liquids.  It  is  not  possible  to  plate  such  structures  by  any 
other  coating  method  than  the  Schoop  Process.  In  such  cases 
tin  or  zinc  may  be  applied  from  dust  or  wire  form  on  all  seams  and 
joints  or  all  over  the  structure,  surfaces  having  been  previously 
cleaned  by  a  light  sand-blasting.  This  treatment  can  be  made  on 
the  parts  of  individual  members  at  the  shops  or  in  the  field  by 
portable  cyclone  and  compressor  outfits  wherever  the  nozzle  of  the 
apparatus  can  be  pointed  normally  to  any  surface.  Proper  initial 
treatment  of  this  kind  or  in  the  field  during  erection  dispenses  with 
all  need  for  repeated  painting. 

Laundry  machinery,  milking  machinery,  dairy  utensils,  water 
heaters,  and  similar  appliances  subject  to  corrosion  can  be  pro- 
tected against  decay  due  to  electrolysis  by  sprayed  deposits  of  zinc 
suitably  located.  The  Schoop  coatings  do  not  compete  in  cost  with 
the  ordinary  tinning  or  galvanizing  applied  to  tonnage  goods  and 
purely  temporary  in  its  effects.  From  the  table  appended,  how- 
ever, showing  the  data  of  gas  consumption  and  total  cost  of  spray- 
ing a  square  foot  .001"  thick  of  all  the  commoner  metals,  it  will 
be  seen  that  tin  and  zinc  can  be  applied  effectively  for  2l/2  cents 
per  square  foot ;  where  zinc  dust  is  applied  by  the  "cyclone"  appa- 
ratus it  can  be  done  for  iy2  cents  per  square  foot. 


G.  Imhoff 

THE  SCUOOP  MKTAL  SPRAY  PROCESS  105 


114 


ISM 


ISM 


a 


T—  i  (X)  CO 
—  H   <M   »O 


<M  10  ^t1  o 

<M(N^>'-<OiO 


OOCOCiOOfNOOCOCD 

oooocooop 


(M  (M  (M  <M  (M 


oooooooo 
cococococccococo 


OO'fO'-HCOO'O 

^rio-^cocoootoo 

CO  CO  CO  CO  t^-  C^l         ^"~< 


qqqqqqqq 

5O  ^H  i— i  LO  <M  iO         *O 

§O  — -i  r— i  O  <— i  (N  C>0 
O  O  O  O  O  O  O 


Cost 
Spray 


(M  CM  C^l  (N  ^H 


(M<M<M(M—  '  T-I  i—  i  1-1 


I-=  E 


(M  (M  <M  Cl  O  00  »O  >O 


I 


000000 


<M  (M  <M  (M  O  (M 

§§§§  ^§ 


&2  g  fe^  «  g.a 

o  a  a  o  <  is:  -j  H 


CHAPTER  XIII 

Tinning  Malleable  Iron  Castings,  Wrought  Iron  and 
Steel 

TO  SIMPLY  give  articles  of  malleable  and  wrought  iron  a 
coating  of  tin  is  a  comparatively  easy  process  to  master, 
but  the  tinning  of  certain  classes  of  hardware  has  reached 
a  high  state  of  perfection,  and  to  tin  saddlery  hardware  and  table 
cutlery  requires  considerable  skill.  The  methods  employed  to  do 
the  work  vary  greatly  in  different  establishments,  and  the  degree 
of  perfection  attained  is  equally  varied.  Work  that  is  tinned  in 
an  indifferent  and  slovenly  manner  is  not  necessarily  done  cheaply, 
as  the  metal  wasted  on  an  article  that  is  roughly  and  imperfectly 
coated  may  be  of  more  value  than  the  slight  saving  in  labor  cost 
obtained  by  rushing  the  work  through  without  giving  proper  at- 
tention to  the  applying  of  a  light  and  even  coating.  The__Jiigh 
p_rice  of  pig  tin  makes  the  material  cost  of  tinning  much  more 
than  the  labor  co-4.  The  use  of  care  in  bringing  the  finished  ar- 
ticles out  free  from  surplus  tin  not  only  adds  greatly  to  the  com- 
mercial appearance  of  the  goods,  but  materially  decreases  the  cost 
of.  the  \vork.  The  most  economical  result  is  obtained  by  careful 
attention  to  the  boat  of  the  tinning  bath  and  to  the  skillful  hand- 
ling "of  the  articles  during  their  removal  Irom  it  and  before  they 
are  cooled.  If  the  tin  is  not  hot  enough  the  articles  will  be  Jieavilv^ 
coated,  and  it  will  cool  on  the  work  bunchy  and  wavy.  Tin  when 
heated  above  a  certain  limit  jilso  causes  a  rough  and  uneven  appear- 
ance OL  the  work,  injures  its  color  and  destroys  the  luster.  The 
use  'of  a  good  pyrometer  in  a  tinning  bath  is  a  great  help  to  the 
operator  in  maintaining  a  proper  and  uniform  heat  of  the  tin. 
Care  in  keeping  the__tin  free  from  dross  or  slag  is  an  important 
point  in  "ootaming  perfect  work  "and  wiil~be~referred  to  in  its 
proper  place. 

Plant  and  Equipment 

When  installing  a  tinning  plant  convenient  arrangement  for 
handling  the  work  should  he  given  all  the  consideration  possible, 
and  the  operator  will  find  it  a  great  help  toward  making  his  work 

106 


TINNING  MALLEABLE  IRON  CASTINGS,  WROUGHT  IRON       107 

easy,  as  well  as  efficient,  if  he  will  study  tojmprove  methods  and 
tools  employed  in  handling  the  various  articles  that  come  to  him 
for  tinning. 

While  it  is  our  purpose  to  treat  the  subject  of  tinning  in  a  man- 
ner that  will  enable  a  novice  to  make  a  successful  beginning,  the 
best  results  can,  of  course,  only  be  reached  by  actual  experience. 
With  the  principles  and  requisites  necessary  to  perfect  results  well 
understood  no  trouble  should  be  experienced  by  one  of  average 
mechanical  ability  in  mastering  the  business. 

To  make  the  different  operations  of  preparing  and  tinning  ar- 
ticles of  malleable  iron,  wrought  iron  and  steel  easily  understood, 
we  shall  treat  each  operation  separately. 

While  the  illustrations  we  gi\e  will  serve  as  a  general  guide  in 
equipping  a  plant,  it  does  not  follow  that  they  cannot  be  changed 
to  suit  local  conditions^  It  would  he  impossible  to  illustrate  here 
the  exact  plan  best  to  follow  in  each  individual  case,  and  those 
undertaking  the  installation  of  a  plant  must  be  governed  to  a  great 
extent  by  their  requirements  as  they  see  them. 

It  should  be  kept  in  mind  when  deciding  what  part  of  the 
factory  can  best  be  devoted  to  the  tinning  department  that  more 
or  less  gases  and  fumes  ^prevaij  while  the  work  is  carried  on.  These 
gases  and  fumes  are  not  only  disagreeable  to  inhale,  but  are  de- 
structive to  fine  machinery,  tools  and  finished  work.  That  the 
work  may  not  become  a  source  of  annoyance  to  those  who  are  not 
immediately  engaged  in  it  or  destructive  to  machinery  and  stock, 
the  tinning  plant  should  be  located  if  possible  in  a  building  by 
itself,  taking  care  to  provide  ^good  ventilation  and  drainage. 

Arpom_devoted  to  this  work  should  not  be  less  than  10  feet  in 
height,  and  it  is  a  good  plan  to  provide  the  kettles  and  acid  tanks 
with  hoods  connected  with  ventilators  to  carry  off  the  fumes^  The 
hoods  should,  of  course,  be  high  enough  to  prevent  interference 
with  the  work  of  the  operators. 

The  illustrations  show  tanks  of  cypress  or  pine  for  containing  the 
different  solutions  used  in  preparing  and  finishing  the  work,  but 
oil  barrels  sawed  in  half  may  be  employed  for  the  purpose  if  they 
are  properly  cleaned  inside,  either  by  burning  or  washing  in  a  hot, 
strong  solution  of  soda  ash  and  water. 

For  heating  the  tin  hard  coal  is  best.,  as  it  gives  the  most  uniform 
heat  and  is  most  easily  controlled.  Soft  coal,  coke,  natural  gas 
and  even  wood  can,  however,  be  employed  for  the  purpose. 


108  GALVANIZING  AND  TINNING 

Plan  of  a  Tinning  Plant 

We  show  in  Fig.  42  a  ground  plan  of  a  tinning  plant  intended 
for  general  work,  except  the  tinning  of  common  cast  iron.  In  this 
illustration  A  is  the  rnno-bino-  kp|,fle — that,  is,  t.hft  kettle  used 


give  the  work  its  first  coating  of  tin;  B  is  the  finishing  kettle- 
C  is  the  tank  containing  muriate  of  xinc;  D  is  what  is  termed  in 


ARRANGEMENT  OF  EQUIPMENT  IN  A  TINNING  PLANT 


the  trade  the  Jlwjijj2Umg  box/'  and  is  simply  an  arrangement  to 
prevent  the  drops  of  molten  tin  being  thrown  promiscuously 
around  the  room  when  the  operator  is  shaking  or  swinging  his 
work  tfc  free  it  from  surplus  metal;  E  is  a  tank  made  of  sheet 
iron  for  containing  the  kerosene  oil  used  to  cool  the  work1  in,  the 
intent  being  to  have  this  tank  surrounded  by  cold  running  water 
to  keep  the  oil  cool,  the  water  being  contained  in  the  companion 
tank  F;^js  a_tank  provided  with  a  steam  coil,  the  intent  being  to 
keep  the""tank  filled  witlfcTean,  hot  water;  in  "which  to  rinse  the 
finished  work  before  drying  it  off  in  the  sawdust^  which  is  con- 
tained in  thejbpjj^j  I  and  _0  are  water  tanks  ..  used  for  storing 
the  work  after  it  has  been  cleaned  in  the  acid;  K  is  a  tank  con- 
taining  muriatic  or  sulphuric  acid;  L  and  M  are  acid  tanks,  the 
use  of  which  will  oe  explained  in  the  proper  place;  N  is  a  tank 
for  containing  a  hot  alkali  solution,  and  it  should  be  provided  with 


TINNING  MALLEABLE  IRON  CASTINGS,  WROUGHT  IRON       109 


a  s Learn  coil;  R  denotes  a  drain  through  the  center  of  the  room 
for  carrying  off  the  waste  water.  A  sectional  plan  of  this  floor  is 
given  in  Fig.  43. 


FIG.  43  —  DETAILS  OF  FLOOR  CONSTRUCTION,  SHOWING  DRAIN 

Tools  and  Kettles 

.  employed  in  handling  the  work  are  very  simple  in  con- 
struction. They  consist  of  wires  forpjH  into  van'mjs  ^happ^  ladles. 
or  baskets  made  from  perforated  sheet  iron  or  wire  cloth,  and  tongs 
with  jaw's"*  formed  to  hold  the  various  articles  to  he  handled  with 
them.'  Those  illustrated  by  Fig.  25  in  chapter  on  galvanizing  will 
be  found  useful  and  all  that  will  be  required  in  many  cases.  The 
ingenuity  of  the  operator  will  readily  suggest  what  tools  are  re- 
quired for  the  work  in  hand. 

The  number  of  tinning  kettles  necessary  depends  altogether  on 
the  class  of  goods  to  be  tinned.  _  The  most  common  kinds  of  hard- 
ware_specialties  can  be  tinned  very  satisfactorily  in  a  single  kettle, 
while  the  better  class  of  tinning,  such  as  saddlery  hardware,  iron 
spoons,  etc.,  require  two  kettles  for  best  results,  and  even  three 
may  sometimes  be  emuloved  to  yond  Rflvanfaorp 


Where  a  plant  is  fitted  up  for  a  fine  grade  of  tinning,  the  kettle 
used  to  give  the  castings  their  first  coating  is  called  a  "roughing" 
kettle,  and  the  other  kettle  or  kettles  the  "finishing-."  When  a 
roughing  kettle  is  used  no  particular  care  is  taken  to  have  the 
articles  come  from  it  smoothly  coated  or  free  from  surplus  tin,  as 


110  GALVANIZING  AND  TINNING 

the  unevenness  of  the  coating  will  be  removed  by  their  treatment 
in  finishing.  The  object  of  the  roughing  kettle  is  to  givejthejron^ 
a  thorough  coating  of  tin,  as  rapidly  as  it  is  prepared  for  receiv- 
ing it,  to  prevent  rusting.  After  the  iron  receives  a  thorough 
roughing  coat  it  may  be  stored  away  until  required  for  finishing. 
"Torthose  having  only  a  small  amount  of  tinning  to  do  it  would 
not  pay  to  invest  in  an  expensive  outfit  of  wet  rolling  barrels,  and 
very  good  results  can  be  obtained  without  them.  In  fact,  only  a 
few  of  the  larger  concerns  engaged  in  tinning  are  so  fitted,  and 
their  work  is  of  a  nature  that  requires  the  best  results  possible  to 
obtain  m  the  way  of  smoothness  and  brightness  of  finish. 


CHAPTER  XIV 

Preparing  the  Work  for  Tinning 

OlfDIXAIiILY  the  common  grades  of  tinned  articles  are 
made  ready   for  tinning  by _s imply  removing  the  sand^ 
scale  or  rust  by  pickling  in  commercial  sulphuric,  muri- 
atic or^Eydronuoric  acid,  but  the  finer  grades  of  work  are  pre- 
irecf  fof~tinning  by  careful  and  lengthy  treatment  in  the  water 
b 


Removing  Scale  and  Rust  with  Sulphuric  Acid 

Before  steel  and  wrought  iron  will  take  a  coating  of  tin  ail 
scale  and  rust  must  be  removed.     This  is  best  accomplished  with  \ 
a  pickle  composed  of  1  part  sulphuric  acid  to  about  30  to  40  of  / 
water,  bringing  the  solution  to  a  temperature  of  about  150  de-  V 
grees  F. 

If  the  articles  are  of  such  shape  that  they  will  pack  closely  to- 
gether they  must  be  stirred  at  intervals  while  pickling  so  the  acid 
will  have  free  action  on  all  parts  alike,  otherwise  the  scale  or  rust 
will  not  be  removed  on  the  parts  that  come  in  contact  with  each 
other,  the  result  being  that  the  acid  will  burn  the  material  ex- 
posed to  the  action  of  the  pickle  before  the  scale  could  possibly 
be  removed  from  the  parts  in  contact. 

In  pickling  sheets  they  must  be  placed  in  racks  that  will  prevent 
one  sheet  lying  against  another.  Sheets  should  be  carefully  in- 
spected, and  any  spots  that  the  acid  has  not  touched  must  be  re- 
moved with  the  aid  of  a  sharp-pointed  steel  tool.  The  shank  of 
an  old  file  ground  to  a  point  and  hardened  answers  the  purpose 
very  well. 

If  the  articles  are  sffl?1]r  and  it  is  dpsirpd  to  give  them  a  fine 
surface,  roll  them  in  gravel  and  water  after  removing  the  scale 
"and  rust  with  the  acid  solution,  jind  to  further  improve  their  sur- 
face give  them  a  second  rolling  in  scraps  of  leather.  The  effect 
of  rolling  is  to  give  the  articles  a  smooth  surface,  and  the  smoother 
the  surface  obtained  iu  preparing,  the  smoother  and  brighter  will 
])e  the  goods  after  tinning. 

We  do  not  wish  it  to  be  understood  that  the  rolling  operation  is 
111 


112  GALVANIZING  AND  TINNING 

absolutely  necessary  to  obtain  a  complete  coating  of  the  goods,  as 
they  will  take  the  tin  perfectly  if  that  operation  is  omitted,  pro- 
vided they  are  properly  cleaned,  but  their  appearance  is  greatly 
improved  by  rolling,  and  when  jtjs__dftsired  to  obtain  the  best 
finish  possible  the  rolling  barrel  must  bo  employed. 

When  the  removal  of  scale  and  rust  has  been  accomplished  and 
the  material  is  perfectly  clean  it  should  be  stored  in  tanks  contain- 
ing clear  water,  there  to  remain  until  the  operator  is  ready  to  put 
it  through  the  subsequent  operations.  Do  not  allow  the  work  to 
remain  in  running  water,  as  it  will  soon  rust  or  oxidize, 

The  operator  must  not  fail  to  examine  the  work  frequently  while 
it  remains  in  the  hot  pickle  to  determine  when  the  desired  result 
has  been  obtained.  If  it  is  allowed  to  remain  too  long  a  time 
after  the  scale  and  rust  have  been  removed  the  acid  will  attack  the 
surface  of  the  material  and  leave  it  rough  and  seamed,  jmper- 
fections  caused  by  overpickling  cannot  be  eliminated  by  the  coating 
of  tin,  and  the  commercial  appearance  of  the  goods  will  be  injured. 

Cleaning  Sandy  Castings  with  Sulphuric  Acid 

Castings  that  have  sand  on  them  must  be  subjected  to  a  treat- 
ment that  will  effectually  remove  it,  as  a  perfect  coating  cannot 
be  obtained  if  sand  remains.  The  removal  of  sand  can  be  ac- 
complished by  placing  the  castings  on  an  inclined  platform  and 
keeping  them  wet  with  a  cold  pickle  composed  of  1  part  sulphuric 
acid  to  6  of  water,  until  the  sand  is  loosened  enough  to  be  washed 
off  by  a  stream  of  water.  From  10  to  20  hours  is  required  to 
accomplish  its  removal,  and  then  a  casting  brush  must  often  be 
employed  to  remove  all  the  small  particles  that  are  burned  in  where 
there  are  sharp  angles. 

Boiling  with  plenty  of  sharp  scratches  or  stars  is  the  only  sure 
way  to  obtain  a  perfectly  smooth,  clean  casting,  and  we  should 
never  attempt  to  tin  malleable  castings  in  any  considerable  quan- 
tity without  the  aid  of  a  rolling  barrel.  As  in  the  case  of  steel  or 
wrought  iron  articles,  the  wet  rolling  barrel  supplemented  by  the 
dry  rolling  in  leather  scraps  fits  the  castings  to  take  a  beautiful 
coating  of  tin  with  a  bright  luster. 

The  platform  on  which  castings  are  placed  for  pickling  with 
sulphuric  acid  should  have  a  tank  placed  under  one  end  at  its 
lowest  point  to  catch  the  acid  as  it  flows  from  the  castings  after 
each  bailing  operation. 


PREPARING  THE  WORK  FOR  TINNING  113 

Cleaning  with  Muriatic  Acid 

The  removal  of  scale  and  rust  from  wrought  iron  and  steel  can 
be  accomplished  by  a  pickle  composed  of  1  part  muriatic  acid  to 
15  to  20  parts  of  water,  but  the  cost  is  greater  and  the  result 
obtained  no  better.  It  is  not  advisable  to  use  this  acid  for  the 
purpose  unless  the  amount  of  work  to  be  treated  is  very  limited 
and  the  sulphuric  acid  pickle  is  not  available. 

In  Fig.  42  K  represents  a  tank  to  be  used  for  the  sulphuric  or 
muriatic  pickle,  and  I  indicates  the  storage  tank  for  the  prepared 
work. 

Cleaning  Sandy  Castings  with  Hydrofluoric  Acid 

We  have  given  the  course  to  be  followed  for  cleaning  sandy 
castings  with  sulphuric  acid,  because  it  may  not  always  be  pos- 
sible to  obtain  hydrofluoric  acid.  Where  it  is  possible  to  substi- 
tute this  powerful  acid  for  sulphuric  it  should  be  employed,  as  its 
action  is  much  more  rapid  and  certain,  and  less  destructive  to  the 
castings. 

In  employing  hydrofluoric  acid  to  remove  sand  make  a  solution 
for  slow  pickling  in  the  proportion  of  1  part  acid  to  30  of  water. 
For  quick  pickling  make  the  proportion  1  of  acid  to  20  of  water. 
Immerse  the  castings  until  the  sand  is  dissolved,  which  will  be  in 
from  15  minutes  to  3  hours,  depending  on  the  strength  and  tem- 
perature of  the  solution  and  the  tenaciousness  of  the  sand. 

A  good  arrangement  for  doing  this  work  is  made  by  two  or  more 
small  tanks  for  containing  the  castings  elevated  by  a  bench  or 
stand  a  few  inches  above  a  larger  tank  containing  the  pickling 
solution.  The  castings  are  covered  by  solution  bailed  from  the 
lower  tank,  which  is  easily  drawn  off  after  the  castings  are  pickled 
by  removing  plugs  fitted  to  holes  in  the  bottoms  of  the  smaller 
tanks.  In  this  way  the  pickling  solution  can  be  used  over  and 
over  again,  while  the  castings  can  be  easily  removed  for  subse- 
quent treatments. 

Water  Rolling 

This  method  of  preparation  not  only  effectually  removes  all  im- 
pediments to  a  perfect  coating,  but  gives  the  articles  a  perfectly 
smooth  surface  on  which  to  deposit  the  tin,  the  degree  of  per- 
fection obtained  being  determined  by  the  time  and  care  expended 
in  the  rolling  operation.  Further  information  on  the  rolling  and 


114  GALVANIZING  AND  TINNING 

tumbling  of  cast,  wrought  and  malleable  iron  to  be  tinned  is 
given  in  Chapter  VI,  pages  51  to  65. 

Removing  Paint  or  Grease 

If  the  work  has  grease  or  paint  on  it,  it  must  be  removed  arid 
the  sand  blast  will  be  found  of  great  value  for  this  work,  although 
a  hot  solution  of  caustic  soda  or  soda  ash  will  often  times  accom- 
plish the  desired  result.  Make  the  solution  very  hot  and  strong, 
and  immerse  the  work  in  it  until  free  from  all  such  matter,  after 
which  rinse  it  thoroughly  in  clean  water.  This  operation  should 
precede  pickling  when  necessary  to  perform  it.  The  tanks  for 
this  purpose  are  designated  in  Fig.  42  as  N  and  0 ;  N  being  the 
caustic  soda  tank  and  0  the  rinsing  tank. 


CHAPTER  XV 


Applying  the  Coating  of  Tin 

AS  ALREADY  stated,  very  good  results  can  be  obtained  by 
simply  using  one  kettle  of  tin  when  the  commercial  ap- 
pearance of  the  work  is  of  secondary  importance.     Where 
only  a  single  kettle  is  employed  the  tin  should  be  maintained  at  a 
temperature  of  about  500  degrees  F.,  and  the  work  may  be  cooled 
m  hot  water  and  dried  off  in  sawdust.  "" 

The  operations  "preliminary  to  dipping  the  work  in  the  tinning 
bath  are  precisely  what  they  would  be  if  more  than  one  kettle  was 
used.  As  these  operations  will  be  explained  in  connection  with 
those  for  using  two  kettles,  we  will  not  give  them  here. 


FIG.  44  —  FRONT  ELEVATION 


FIG.  45 — SIDE  ELEVATION 


Details  of  Tinning  Kettle 

Where  only  a  single  kettle  is  employed  more  or  less  trouble  will 
be  experienced  in  keeping  the  dross  or  slag  which  rises  to  the  sur- 
face of  the  tin  from  adhering  to  the  work,  and  in  keeping  the  tin 
at  a  uniform  temperature.  The  dross  or  slag  must  be  removed 
from  the  tin  frequently  with  a  perforated  skimmer,  and  when  the 
black  flux  that  forms  on -the  surface  of  the  tin  from  the  muriate 
of  zinc,  in  which  the  castings  are  dipped  previous  to  immersing 

115 


116  GALVANIZING  AND  TINNING 

them  in  the  molten  tin,  becomes  present  in  sufficient  quantities 
to  interfere  with  drawing  the  work,  it  must  also  be  removed  in 
part.  A  small  amount  aids  in  the  work,  but  when  it  accumulates 

in  a  sufficient  quantity  to 
catch  on  the  work  as  it  is 
drawn  out  it  is  apt  to  stain 
the  work  and  leave  white 
streaks  wherever  it  touches. 
The  cooling  water  should 
also  l>e  kept  clean  and  free 
from  acid.  If  it  is  not,  the 
work  is  liable  to  be  discol- 

ored  and  rust.    In  Figs.  44, 
FIG.  46— PLAN  AT  GRATE  LINE 

45  and  46  we  show  manner 

of  bricking  in  a  single  kettle,  the  casting  details  being  shown  in 
Fig.  47. 


a 


TIG.  47  —  CASTINGS  REQUIRED  FOB  TINNING  KETTLE 

Tinning  with  Two  or  More  Kettles  of  Tin 

When  the  work  has  been  made  perfectly  clean  and  free  from 
sand,  scale,  rust,  grease  or  paint  by  some  one  of  the  treatments 
described,  it  is  ready  for  the  final  operations.  If  the  work  is  of 
a  kind  that  will  admit  of  its  being  strung  on  wires,  use  such  wires 
as  seem  best  adapted  to  the  work  in  hand.  For  many  kinds  of 
work  a  piece  of  wire  bent  in  the  shape  of  a  croquet  wicket,  but 
larger,  will  be  just  the  thing.  Good  stiff  wires  should  be  used,  and 
they  should  be  long  enough  to  allow  plenty  of  room  for  the  operator 


i/. 


APPLYING  THE  COATING  OF  TIN  11? 

to  grasp  the  ends  without  being  burned.  That  is  to  say,  if  you 
have  10  inches  of  tin  in  the  kettle,  make  the  end  of  the  wire  20 
inches  long,  which  will  allow  10  inches  of  wire  out  of  the  tin 
where  the  operator  can  grasp  it  when  he  is  ready  to  draw  the  work 
from  the  kettle.  Provide  plenty  of  these  wires  so  that  the  hand- 
ling of  the  work  may  be  facilitated. 

String  on  wires  as  much  of  the  work  as  you  think  you  can 
handle  comfortably,  and  put  them,  several  strings  at  a  time,  into 
the  alkali  solution.  The  work  may  be  allowed  to  remain  in  this 
solution  for  several  minutes,  or  while  the  operator  is  filling  more 
wires.  From  the  alkali  solution  the  work  is  to  be  passed  into  the 
rinsing  tank,  where  care  should  be  taken  that  all  traces  of  the 
alkali  are  removed. 

When  this  is  accomplished  the  work  is  to  be  given  a  few  minutes' 
immersion  in  a  solution  of  muriatic  acid  and  water.  This  mix- 
ture should  be  in  the  proportion  of  1  of  acid  to  4  or  5  of  water  in 
cold  weather,  while  in  warm  weather  8  or  10  of  water  to  1  of  acid 
will  do  the  required  work.  The  object  of  this  dip  is  to  remove 
any  trace  of  rust  that  may  have  formed  on  the  work.  The  tank 
for  this  purpose  is  designated  as  K  in  Fig.  42,  and  for  many  kinds 
of  work,  such  as  castings  that  have  been  cleaned  by  dry  rolling,  and 
goods  made  of  material  that  has  no  scale,  all  that  is  necessary  is 
to  give  it  a  few.  minutes'  immersion  in  this  solution. 

After  this  last  dip  of  muriatic  acid  and  water,  which  by  the  way 
should  never  be  omitted,  the  work  is  to  be  dipped  in  muriate  of 
zinc,  which  is  the  last  dip  previous  to  immersing  it  in  the  molten 
tin.  Tank  C,  Fig.  42,  is  used  to  contain  the  muriate  of  zinc, 
which  solution  is  made  by  dissolving  scraps  of  zinc  in  clear  muri- 
atic acid. 

Passing  the  Work  Through  the  Tinning  Kettle 

If  two  kettles  of  tin  are  in  use,  as  shown  in  Fig.  42  by  A  and 
B,  take  a  wire  full  of  work  to  be  dipped  and  plunge  it  while  wet 
with  muriate  of  zinc  into  the  tin  in  the  roughing  kettle,  desig- 
nated in  Fig.  42  as  A.  Put  several  strings  of  work  into  the  kettle 
at  once  and  allow  them  to  remain  until  the  work  is  as  hot  as  the 
tin,  which,  in  this  kettle,  should  be  maintained  at  a  heat  of  about 
500  degrees  F. 

After  the  work  has  remained  in  the  roughing  kettle  for  the  re- 
quired time  take  a  wire  full  in  the  left  hand,  and  with  a  skimmer 


118  GALVANIZING  AND  TINNING 

in  the  right  hand  clear  a  space  on  the  surface  of  the  tin  large 
enough  to  permit  the  wire  full  of  work  being  removed  without  any 
of  the  dross  or  flux  adhering  to  it.  Remove  the  wire  full  of  work 
and  pass  it  directly  to  the  second  kettle.  It  is  not  necessary  to 
shake  off  the  surplus  tin  when  removing  work  from  the  first  ket- 
tle, but  it  is  necessary  to  use  care  that  none  of  the  flux  or  slag  is 
carried  over  to  the  second  kettle  on  the  work. 

While  retaining  hold  of  the  wire  the  operator  allows  the  work 
to  remain  in  the  second  kettle  for  a  fraction  of  a  minute  until  the 
heat  of  the  work  attained  in  the  first  kettle  is  reduced  to  about  the 
temperature  of  the  tin  in  the  second  kettle,  which  for  most  purposes 
should  be  about  400  degrees  F.  Very  small  articles  may  require 
that  the  tin  in  the  second  kettle  attain  a  temperature  of  450  de- 
grees F.  A  little  higher  heat  will  cause  the  tallow,  which  is  on 
the  surface  of  the  second  kettle,  to  a  depth  of  £  to  1  inch,  to 
ignite.  When  the  work  has  about  reached  the  heat  of  the  metal 
draw  it  quickly  from  the  tin,  and  after  a  few  rapid  swinging  mo- 
tions to  free  it  of  surplus  metal  plunge  it  into  the  tank  of  kerosene 
oil,  using  motions  calculated  to  keep  the  articles  from  sticking  to- 
gether. A  little  practice  will  soon  determine  what  motion  is  best 
for  keeping  the  articles  separated  and  preventing  lumps  of  tin 
from  forming  on  the  work. 

D  in  Fig.  42  denotes  the  position  of  the  box  provided  to  catch 
the  drops  of  surplus  tin  that  are  thrown  from  the  work  as  the 
operator  swings  it  to  and  fro.  E  denotes  the  tank  for  containing 
kerosene  used  for  cooling,  as  already  explained,  and  this  tank 
should  be  surrounded  by  running  water  to  prevent  the  oil  heating 
to  a  point  where  it  would  ignite. 

The  work  should  be  allowed  to  remain  in  the  oil  long  enough  to 
set  the  coating  of  tin,  and  should  then  be  dipped  in  hot  water  and 
thrown  into  fine  dry  sawdust  to  dry  it  and  remove  the  oil.  If  the 
articles  are  very  heavy  it  may  be  necessary  to  plunge  them  into 
cold  water. after  the  oil. 

If  small  work  cannot  be  strung  on  wires  a  "basket"  may  be  used 
for  dipping  it.  The  basket  may  be  made  of  sheet  iron,  in  which 
case  it  should  be  well  perforated  to  allow  the  tin  to  escape,  or  it 
may  be  made  of  wire  cloth  of  a  mesh  sufficiently  small  to  prevent 
the  work  falling  through.  Fig.  25  illustrates  the  shape  of  these 
baskets,  which  are  designated  as  A  and  B.  Nails,  tacks,  rivets  and ' 
all  similar  small  articles  are  tinned  by  means  of  these  baskets. 


APPLYING  THE  COATING  OF  TIN  11& 

Tongs  are  used  for  handling  heavy  articles,  but  those  used  in  the 
tin  should  not  be  used  for  cooling  the  work,  as  they  would  mark 
it.  The  tongs  used  for  cooling  should  not  be  put  into  the  molten 
tin.  The  shape  of  tongs  should  be  made  to  suit  the  form  of  the 
article  to  be  handled. 

Tinning  Wire  in  Coils 

In  large  manufacturing  establishments  machinery  is  employed 
with  which  several  strands  of  wire  are  passed  through  the  tinning 
kettle  simultaneously.  To  do  the  work  on  a  small  scale,  provide 
reels  that  will  accommodate  a  coil  of  wire.  Place  one  of  the  reels 
in  a  position  where  the  black  wire  will  pass,  as  it  is  uncoiled, 
through  a  tank  containing  muriate  of  zinc  through  the  kettle  of  tin. 
The  other  reel  should  be  placed  in  a  position  where  it  will  coil  up 
the  wire  as  it  is  drawn  out  of  the  tin.  The  reel  used  to  draw  the 
wire  through  the  kettle  must,  of  course,  be  provided  with  an  ar- 
rangement for  revolving  it,  and  a  device  to  hold  the  wire  under  the 
muriate  of  zinc  and  also  under  the  tin  as  it  passes  through  must 
be  employed.  As  the  necessary  arrangement  will  readily  suggest 
itself  we  do  not  think  it  necessary  to  illustrate  it. 

At  the  point  where  the  wire  leaves  the  molten  tin  a  piece  of 
tow  is  twisted  around  the  strand,  sufficiently  tight  to  wipe  off  the 
surplus  metal,  which  flows  back  into  the  kettle.  If  the  wire  is 
very  heavy  it  must  pass  through  water  after  it  leaves  the  tin,  the 
water  tank  being  placed  where  the  wire  will  not  enter  it  until  it 
has  passed  through  the  bunch  of  tow  used  for  wiping  off  the  sur- 
plus metal. 

If  the  wire  is  covered  with  a  heavy  scale  or  rust  it  must  be 
cleaned  in  sulphuric  acid  the  same  as  any  other  wrought  iron  or 
steel.  If  it  is  bright  wire  all  that  is  necessary  is  to  immerse  it 
in  a  solution  of  muriatic  acid  and  water,  1  part  acid  to  6  of  water. 
If  wire  is  to  be  tinned  in  large  quantities  a  long,  shallow  kettle  is 
best  adapted  to  the  purpose. 

Tinning  Steel  Spoons  and  Similar  Articles 

For  this  purpose  provide  a  good  sized  kettle  for  "roughing"  the 
work —  that  is,  for  giving  the  first  coating.  For  finishing  the 
work  use  small  kettles.  A  kettle  15  inches  long,  8  inches  wide  and 
6  inches  deep  is  amply  large  for  finishing  work  of  this  kind.  We 
refer  to  a  plant  fitted  especially  for  this  business.  The  work  can 


120  GALVANIZING  AND  TINNING 

be  done  in  an  outfit  such  as  we  illustrate  by  Fig.  42,  but  large 
finishing  kettles  are  not  as  well  adapted  to  this  business  as  small 
ones,  as  the  tin  in  a  large  kettle  is  apt  to  become  dull  in  color  by 
constant  use,  while  in  a  small  kettle  the  tin  is  renewed  more  often, 
which  allows  it  to  hold  its  color  much  better. 

In  preparing  the  articles  they  should  be  rolled  in  tumbling  bar- 
rels with  scraps  of  leather  and  then  carefully  cleaned  in  an  alkali 
solution.  After  rinsing  off  the  alkali  they  should  be  immersed  in 
quite  a  strong  solution  of  muriatic  acid  and  water  for  five  or  ten 
minutes,  and  then  dipped  in  the  roughing  kettle  by  means  of  a 
wire  basket,  first  dipping  the  work  in  a  solution  of  muriate  of 
zinc.  As  soon  as  they  are  thoroughly  coated  shake  them  out  of 
the  basket  in  such  a  way  as  to  insure  the  separation  of  as  many 
as  possible.  It  makes  no  difference  whether  they  come  smooth  or 
not  so  long  as  they  are  thoroughly  coated.  The  smoothness  will 
come  in  the  finishing  operation. 

To  finish  the  goods  take  one  piece  at  a  time  in  a  pair  of  tongs 
adapted  to  holding  them  and  immerse  them  in  the  finishing  kettle, 
the  tin  in  which  is  covered  with  beef  tallow  to  the  depth  of  about 
\  inch.  As  soon  as  the  article  reaches  the  same  heat  as  the  tin 
remove  it  and  allow  it  to  cool  until  the  tin  will  not  run,  after 
which  wipe  off  the  goods  in  flour. 


CHAPTER  XVI 

Re-Tinning 

HE  term  re-tinning  refers  to  the  re-coating  of  pressed  or 
stamped  ware  with  tin.  In  the  process  of  manufacturing 
tinware  from  tin  plate  6y  stamping  or  pressing,  the  origi- 
nal coating  on  the  sheets  is  partly  destroyed;  hence,  it  becomes 
necessary  to  "re-tin"  them:  i.e.,  give  them  another  coat  of  tin. 
It  requires  no  little  amount  of  skill  to  operate  a  re-tinning  plant 
successfully,  and  satisfactory  results  are  only  obtained  after  long 
practice.  For  this  reason,  we  omitted  any  extended  mention  of 
the  art  of  re-tinning  in  the  first  issue  of  "Galvanizing  and  Tin- 
ning." Since  the  book  was  published,  however,  we  have  had  so 
many  communications  from  parties  seeking  information  on  the 
subject  that  we  have  decided  to  try  and  explain  the  process  to  the 
best  of  our  ability.  While  perhaps  our  explanation  will  not  enable 
the  unskilled  to  successfully  operate  a  re-tinning  plant,  it  is  hoped 
that  what  we  have  to  say  on  the  subject  will  not  only  prove  of 
assistance  to  the  novice,  but  to  those  already  engaged  in  the 
business. 

Plant  and  Equipment 

The  illustrations  show  the  construction  of  a  re-tinning  stack 
without  going  into  dimensions,  as  the  dimensions  of  the  various 
kettles  can  only  be  determined  by  the  class  of  work  that  it  is 
desired  to  handle.  We  might  say,  however,  that  our  illustrations 
of  the  kettles  and  brickwork  of  a  re-tinning  stack  were  made  from 
a  plant  in  operation  on  re-tinning  ordinary  kitchen  ware,  such  as 
pressed  dish  pans,  wash  basins,  etc.,  etc. ;  the  actual  dimensions 
of  the  kettles  designated  as  A  and  C  in  Fig.  48  being  30"  square. 
The  dimensions  of  the  kettle  shown  in  the  same  Figure  as  B  are 
24"  wide,  30"  long  and  24"  deep,  while  the  small  kettle  desig- 
nated as  D,  known  as  the  "listing"  kettle,  is  6"  wide,  12"  long 
and  from  3"  to  4"  deep. 

As  indicated  by  Figs.  48  and  49  the  outfit  for  a  re-tinning  plant 
consists  of  four  kettles.  A  is  what  is  known  as  the  "soaking" 
kettle,  and  is  used  to  contain  molten  beef  tallow.  B  contains  the 

121 


122 


GALVANIZING  AND  TINNING 


molten  tin  and  is  known  as  the  -tinning"  kettle.  C  contains  beef 
tallow  and  is  known  as  the  "finishing"  kettle,  while  D  contains 
molten  tin  and  is  known  as  the  "listing"  kettle. 

The  soaking  kettle  A  contains  beef  tallow.  In  this  kettle  are 
immersed  in  rotation  articles  to  be  re-tinned.  When  the  goods 
are  received  in  the  re-tinning  room  from  the  stamping  room  for 


FIG.  48 — RE-TINNING  FURNACE 

re-tinning,  they  are  covered  with  various  substances  that  have 
been  vsed  in  the  stamping  room  to  facilitate  the  stamping  opera- 
tion. This  foreign  substance  usually  consists  of  a  solution  of 
grease  and  soap,  which  must  be  removed  before  the  articles  are 
in  proper  condition  for  re-tinning.  The  soaking  kettle  is  required 
not  only  for  the  removal  of  all  foreign  substance  that  has  accum- 
ulated on  the  articles  in  the  process  of  stamping,  but  to  bring 
them  to  the  proper  heat  for  immersing  in  the  tinning  kettle  B. 
In  order  to  have  the  work  proceed  uniformly  and  systematically 
the  soaking  kettle  A  is  provided  with  a  rack  or  container,  the 
general  construction  of  which  we  illustrate  by  Fig.  50.  The  in- 
tent of  these  racks  or  containers  is  to  prevent  the  articles  from 
"nesting"  together  in  the  soaking  kettle,  thus  retarding  or  entirely 


RE  TINNING 


123 


defeating  the  object  for  which  this  kettle  is  used.  Hence,  it  is 
obvious  that  these  racks  or  containers  must  be  made  with  a  view 
to  the  proper  accommodation  of  the  articles  to  be  handled.  For 
instance,  what  is  known  to  the  trade  as  a  six-quart  pan  would 
require  a  rack  or  container  of  a  different  size  'than  would  be 
used  for  a  pan  or  article  twice  its  size.  The  rack  or  container 


FIG.  49 — PLAX  OF  RE-TTSXTNG 


has  another  use;  viz.,  that  of  preventing  articles  touching  the 
sides  of  the  kettle  itself  or  sinking  to  the  bottom  and  coming  in 
contact  with  the  refuse  matter  that  has  been  removed  from  them 
in  the  process  of  "soaking."  In  this  connection  we  will  explain 
that  whatever  foreign  substance  is  removed  from  articles  sub- 
jected to  the  "soaking"  process  settles  to  the  bottom  of  the  kettle 
and  in  time  becomes  so  hard  that  it  is  necessary  to  use  consid- 
erable force  to  remove  it.  It  often  requires  the  use  of  a  sharp  bar 
to  detach  it  from  the  kettle.  The  removal  of  this  sediment  is 
something  that  must  be  done  at  intervals  of  probably  two  or  three 
weeks,  although  it  may  be  found  necessary  on  rare  occasions  to 
effect  its  removal  at  more  frequent  intervals. 

There  are  certain  classes  of  stamped  ware  that  do  not  require 
being  held  apart  in  the  soaking  kettle  by  a  device  such  as  we 
illustrate  by  Fig.  50,  for  the  reason  that  their  construction  effec- 
tually prevents  them  from  "nesting"  together  tightly  or  in  such 


124 


GALVANIZING  AND  TINNING 


a  way  that  the  hot  tallow  in  the  soaking  kettle  could  not  readily 
effect  the  removal  of  whatever  foreign  matter  has  accumulated  in 
the  "stamping"  or  "spinning"  process.  The  operator  will  readily 
understand  that  dishes  with  handles  could  not,  owing  to  their 

construction,  "nest"  closely 
together.  In  such  cases  it 
is  only  necessary  to  use  a 
rack  or  container  that  will 
effectually  prevent  the  ar- 
ticles from  settling  to  the 
bottom  of  the  kettle  or  com- 
ing in  contact  with  its  sides. 
If  the  articles  being  treated 
do  come  in  contact  with  the 
sides  of  the  kettle  they  are 
apt  to  be  burned,  which 
might  effectually  prevent 
their  taking  the  tin,  or  they 

FIG.  50-RACK  FOR  INNING  SMALL  WORK  miSht  become  badly  fouled 

with  the  sediment  by  touch- 
ing the  bottom  of  the  kettle.  Where  division  racks  in  the  con- 
tainer are  not  necessary,  a  wire  basket  of  suitable  size  can  be  used. 
It  is,  of  course,  necessary  to  construct  this  wire  basket  or  container 
in  a  way  to  obviate  danger  from  the  conditions  just  described. 

We  have  described  the  intent  and  use  of  the  soaking  kettle  at 
considerable  length  for  the  reason  that  on  its  proper  use,  or,  per- 
haps we  should  say,  upon  the  proper  preparation  of  the  articles 
in  the  soaking  kettle,  depends  almost  entirely  the  success  of  sub- 
sequent operations.  As  the  soaking  process  proceeds  the  supply 
of  tallow  in  the  kettle  decreases;  hence,  it  is  necessary  to  add 
fresh  tallow  from  time  to  time  as  the  work  goes  on,  or  as  fast 
as  it  is  lost  by  evaporation,  or  burned,  it  often  being  ignited  from 
over-heating.  It  also  often  happens  that  the  tallow  will  ignite 
when  the  racks  are  removed  at  the  end  of  the  day's  work,  and, 
owing  to  this  constant  danger  of  fire,  the  several  kettles  must 
be  provided  with  tight  covers,  which  constitute  the  most  practicable 
way  by  which  the  flames  can  be  smothered. 

Where  articles  are  being  treated  that  require  the  use  of  racks 
or  containers,  a  sufficient  number  should  be  used  to  insure  constant 
and  rapid  operation.  As  from  four  to  five  minutes'  immersion  in 


RE-TINNING  125 

the  soaking  kettle  is  required  on  work  stamped  from  heavy  sheets, 
a  sufficient  quantity  of  containing  racks  should  be  provided  to 
insure  uninterrupted  operation ;  viz.,  enough  so  that  the  operator 
will  always  have  a  pan  in  the  soaking  kettle  in  proper  condition 
for  immersion  in  the  tinning  kettle.  It,  of  course,  necessarily  fol- 
lows that  after  the  container  is  once  filled  the  operator  replaces 
articles  as  fast  as  removed  with  others. 

The  kettle  designated  as  B  is  for  containing  the  molten  tin  in 
which  the  work  is  immersed  after  it  has  been  prepared  in  the 
soaking  kettle  A.  The  method  commonly  used  is  to  have  the  man 
operating  the  soaking  kettle  pass  the  articles  as  fast  as  they  are 
prepared  over  to  the  operator  at  the  tinning  kettle;  using  for  the 
purpose  a  pair  of  tongs  of  proper  construction,  or,  perhaps  we 
should  say,  of  proper  shape,  meaning  of  a  shape  fitted  to  the 
article  and  one  that  will  not  have  a  tendency  to  bruise  or  break 
it.  When  the  operator  on  the  soaking  kettle  has  removed  an 
article  from  his  kettle  he  immediately  immerses  it  in  the  tin  con- 
tained in  the  kettle  B,  drawing  it  up  and  leaving  it  on  the  sur- 
face of  the  tin  to  be  handled  by  the  tinner,  who  grasps  it  with 
suitable  tongs  and  again  immerses  it  in  the  tin,  manipulating  it 
rapidly  and  in  such  a  way  as  to  prevent,  so  far  as  possible,  any 
dross  or,  as  it  is  termed  by  tinners,  "scruff"  from  attaching  itself 
to  the  article  being  handled.  At  this  point  the  skill  and  experi- 
ence of  the  operator  is  exercised  in  keeping  the  tallow,  which  has 
been  carried  over  from  the  soaking  kettle,  from  attaching  itself 
to  the  article  being  handled.  We  cannot  very  well  describe  the 
motions  necessary  to  accomplish  this  object,  as  they  can  only  be 
learned  by  experience.  We  wish  to  make  it  plain,  however,  that 
under  no  conditions  must  any  of  the  grease  from  kettle  A  or  B  be 
allowed  to  be  carried  over  into  kettle  C,  as,  in  such  a  case,  the 
contents  of  kettle  C  would  be  so  badly  contaminated  that  it  would 
be  impossible  to  produce  good  and  satisfactory  work.  After  the 
tinner  who  operates  kettle  B  has  accomplished  the  act  of  prop- 
erly removing  the  article  in  hand  from  the  tin  kettle  B  he  places 
it  in  kettle  C,  which  has  been  provided  with  racks  for  the  holding 
of  such  articles  as  racks  are  necessary  for  in  kettle  A.  Even 
the  proper  transferring  of  articles  from  kettle  B  to  kettle  C 
requires  no  little  amount  of  ingenuity  and  experience.  The  im- 
mersion of  articles  from  kettle  B  into  kettle  C  must  be  accom- 
plished without  rippling  or  disturbing  the  finishing  tallow  in  ket- 


128  GALVANIZING  AND  TIXX1NG 

tie  C  more  than  necessary,  and  the  removal  of  articles  from  the 
finishing  grease  in  kettle  C  must  be  accomplished  in  the  same 
careful  manner ;  viz.,  so  as  not  to  disturb  or  agitate  the  hot  grease. 

While  it  is  essential  that  the  tallow  in  the  finishing  kettle  be 
kept  clean  and  maintained  at  a  uniformly  proper  heat,  the  best 
results  are  obtained  after  the  tallow  has  been  used  for  a  time.  In 
fact,  satisfactory  results  cannot  be  obtained  if  the  grease  in  this 
kettle  contains  too  great  a  percentage  of  new  tallow,  or,  as  the 
operator  would  say,  is  too  "sharp,"  meaning  that  if  the  tallow  is 
too  fresh  and  new  the  finished  work  will  either  be  streaked  or 
have  the  coating  removed  in  places.  As  the  object  of  this  ket- 
tle is  to  remove  all  surplus  tin  possible,  it  will  readily  be  seen 
that  it  is  necessary  to  bail  out  the  tin  which  accumulates  in  the 
bottom  of  the  kettle  at  frequent  intervals.  In  large  plants  this 
is  usually  done  at  the  end  of  the  day's  work,  at  which  time  all 
the  tallow  in  the  kettles  A  and  C  is  removed,  principally  to  obviate 
the  danger  of  its  igniting  through  the  night,  at  which  time  the 
fires  are  usually  in  charge  of  the  watchman. 

As  each  article  is  removed  from  kettle  C  the  operator  holds  it 
in  a  position  that  will  permit  of  what  little  surplus  tin  is  left 
running  to  a  given  point,  so  as  to  permit  its  removal.  This  is 
accomplished  by  using  a  short  rod  of  iron  that  is  kept  constantly 
immersed  in  the  listing  kettle.  As  soon  as  the  drop  has  formed, 
and  before  it  has  time  to  harden,  the  operator  takes  the  rod  from 
the  listing  kettle  in  his  left  hand  and  draws  it  quickly  and  evenly 
over  the  place  where  the  drop  of  tin  has  formed,  much  in  the  same 
way  that  a  tinsmith  would  remove  solder  with  his  soldering  cop- 
per. This  explains  the  use  of  the  listing  kettle  D.  It  is  simply 
used  for  containing  sufficient  tin  in  a  molten  state  for  immersing 
the  end  of  the  listing  rod,  so  that  it  will  always  be  handy  and  in 
proper  condition  for  removing  the  drops  of  tin  as  they  form  on 
the  finished  work. 

The  proper  degrees  of  heat  for  the  contents  of  the  different 
kettles  can  only  be  determined  by  experience  and  practice.  The 
tallow  in  the  soaking  kettle  A  must  be  maintained  at  very  close 
to  the  heat  of  the  molten  tin  in  the  tinning  kettle  B,  and  it  is 
obvious  that  the  tallow  in  the  finishing  kettle  C  must  also  be 
maintained  at  approximately  the  same  temperature. 

No  more  than  two  articles  should  be  immersed  in  the  finishing 
kettle  at  one  time.  If  there  are,  one  \y  almost  sure  to  be  spoiled. 


RE-TINNING  127 

As  we  have  explained,  this  finishing  kettle  C  is  used  for  remov- 
ing the  surplus  tin,  and  for  this  reason  is  called  by  tinners  the 
"skinning"  kettle. 

In  handling  very  large  work  the  racks  or  containers  are  left 
out  of  the  soaking  kettle,  and  in  their  place  a  sheet  of  tin  is 
dropped  into  the  bottom  of  the  kettle  so  as  to  keep  the  articles  off 
the  bottom.  This  sheet  should  be  taken  out  at  night. 

As  fast  as  the  work  receives  the  finishing  touches  from  the  man 
operating  the  finishing  kettle,  it  is  placed  on  racks  and  allowed  to 
remain  there  until  it  is  cool  enough  to  be  handled  by  the  operators 
who  give  it  the  final  finish.  The  finishing  force  for  a  re-tinning 
stack  usually  consists  of  three  girls.  For  their  use  a  long  bench, 
E,  Fig.  49,  is  provided.  The  first  operator  gives  the  work  a 
thorough  rubbing  in  dry  soft  sawdust  contained  in  box  F.  The 
second  goes  through  the  same  operation  with  swadust,  mixed  with 
what  is  known  as  "middlings"  or  wheat  bran,  and  contained  in 
box  G,  while  the  third  performs  the  same  operation  with  a  cheap 
grade  of  flour,  contained  in  box  H.  From  there  it  is  finished 
at  the  wiping  bench  J. 

We  will  say,  in  a  general  way,  that  it  is  not  necessary  to  im- 
merse articles  that  are  to  be  re-tinned  in  acid  unless,  by  chance, 
they  have  become  rusty  through  carelessness  in  some  operation  or 
by  letting  them  stand  too  long  after  leaving  the  stamping  ma- 
chines. When  it  is  necessary  to  remove  rust  by  the  use  of  acid, 
the  articles  must  afterward  be  thoroughly  rinsed  in  clean  water, 
after  which  they  should  be  dipped  into  boiling  hot  water  and 
carefully  and  thoroughly  dried  by  the  use  of  sawdust. 

In  providing  tongs  for  handling  the  work  through  the  various 
kettles,  onlv  those  made  of  steel  should  be  used,  and  they  should 
be  carefully  cleaned  and  coated  with  tin  before  being  used.  Care 
should  be  taken  to  select  tongs  suited  to  the  variety  of  shapes 
being  handled. 

As  dross  forms  in  the  tinning  kettle  very  rapidly,  it  is  neces- 
sary to  take  measures  to  prevent  its  interfering  with  the  work. 
This  is  done  by  an  operation  known  as  "boiling"  the  tin,  and  is 
1  accomplished  by  forcing  a  large  block  of  green  wood,  preferably 
S  wjiitejoine,  to  the  bottom  of  the  tinning  kettle  and  causing  it  to 
remain  there  the  desired  time  by  some  simple  device  adapted  to 
the  purpose,  usually  by  means  of  a  rod  of  iron  inserted  in  a  hole 
bored  in  the  block.  These  blocks  of  green  wood  should  be  previ- 


128  GALVANIZING  AND  TINNING 

ously  dipped  in  hot  tallow ;  otherwise,  they  would  cause  the  molten 
tin  to  spatter  in  all  directions  when  the  blocks  were  immersed. 

In  order  to  facilitate  the  removal  of  the  kettles  from  the  brick 
work  when  it  is  necessary  to  replace  them  for  any  purpose,  and 
also  to  assist  in  the  removal  of  the  containers  in  the  several  kettles 
when  it  is  desirable  to  remove  them,  a  strong  bar  of  iron  should 
be  built  into  the  stack  high  enough  to  permit  the  use  of  a  chain 
hoist.  A  few  bars  or  rods  of  iron  should  also  be  built  into  the 
stack  above  the  kettles,  on  which  sheet  iron  can  be  laid  to  pre- 
vent the  soot  that  gathers  in  the  stack  from  falling  into  the  ket- 
tles and  thus  spoiling  the  contents. 

Fig.  48  is  a  sectional  elevation  of  a  re-tinning  stack,  and,  as 
shown  by  Fig.  49,  the  kettles  are  fired  on  the  opposite  side  from 
where  the  workmen  stand  when  operating  the  kettles.  In  order 
to  have  easy  access  to  the  fires  and  to  facilitate  the  removal  of 
ashes,  a  pit  is  provided  which  should  be  large  enough  to  attain 
its  object.  The  depth  of  the  pit  is  governed  entirely  by  the  depth 
of  the  kettles. 

It  will  be  observed  by  referring  to  Fig.  48  that  the  kettles  are 
heated  on  the  sides,  as  well  as  on  the  bottoms,  which  is  accom- 
plished by  means  of  spiral  flues  designated  as  K :  these  spiral  flues 
having  an  outlet  into  the  large  flue  L,  shown  in  Fig.  49,  and 
which  is  a  separate  flue  from  the  one  designed  to  carry  off  the 
fumes  and  smoke  rising  from  the  kettles. 


CHAPTER  XVII 

Tinning  Gray  Iron  Castings 

ONLY  a  few  years  ago  all  articles  used  in  the  preparation 
of  food  which  were  made  of  gray  iron  were  zinc  coated  or 
galvanized,  as  they  could  not  be  tinned  satisfactorily.  This 
fact,  and  the  fact  that  tin  was  a  much  more  desirable  metal  than 
zinc  for  coating  articles  used  for  culinary  purposes,  was  largely 
responsible  for  a  method  of  tinning  gray  iron  which  was  perfected 
by  the  author.  To-day  it  is  almost  impossible  to  sell  zinc-coated 
articles  used  in  the  preparation  of  food,  as  such  articles  made  of 
gray  iron  are  now  tinned  extensively.  For  example,  ice  cream 
freezers,  lemon  squeezers,  meat  cutters,  bread  and  cake  mixers, 
egg  beaters,  fruit  stoners,  vegetable  cutters,  etc.,  made  wholly  or 
in  part  of  gray  iron  and  tinned  are  now  sold  universally. 

In  addition  to  the  uses  to  which  tinned  gray  iron  is  put  by 
the  manufacturers  of  kitchen  and  other  hardware  specialties,  it 
has  been  found  of  great  advantage  to  give  articles  of  cast  iron 
that  are  to  be  copper  or  brass  plated  a  coating  of  tin  previous  to 
plating  them.  The  advantages  come  from  the  lessened  quantity  of 
material  necessary  to  use  in  electroplating,  the  preventing  of 
"leaking"  or  "sweating,"  so  common  where  the  plating  is  deposited 
directly  on  the  bare  casting,  and  also  from  giving  the  articles  the 
appearance  of  spelter  or  brass  castings. 

By  this  process  gray  iron  castings  are  prepared  for  tinning  by 
rolling  them  in  a  solution  of  muriatic  acid,  sal  ammoniac  and 
water,  the  rolling  barrel  being  constructed  to  retain,  under  pres- 
sure, the  gas  formed  by  the  chemicals  used.  The  use  of  this  bar- 
rel makes  it  desirable  to  locate  the  tinning  plant  in  a  building  by 
itself,  as  the  gas  generated  is  constantly  escaping,  carrying  with  it 
quantities  of  the  solution.  At  the  best  the  rolling  room  for  gray 
iron  tinning  is  a  wet,  dirty  place,  and  the  entire  operation  re- 
quires the  use  of  considerable  vater. 

Plant  and  Equipment 

In  erecting  a  building  for  this  purpose  particular  attention  should 
be  paid  to  ventilation  and  drainage.  A  plan  for  constructing  a 

129 


130 


GALVANIZING  AND  TINNING 


floor,  with  a  view  to  perfect  drainage,  is  shown  by  Fig.  43.  Two 
or  more  kettles  (depending  on  the  nature  of  the  work),  set  after 
the  plan  illustrated  by  Figs.  52,  53  and  54  and  various  tanks  built 
after  Fig.  24.,  complete  the  outfit.  The  arrangement,  of  the  outfit 


FIG.  51 — ARRANGEMENT  OF  TINNING  PLANT 

is  shown  by  Fig.  51,  in  which  A  is  the  rolling  barrel  for  preparing 
the  castings  for  tinning.  B  is  a  tank  to  receive  the  castings  after 
they  have  been  treated  in  the  rolling  barrel  A.  This  tank  should 
be  provided  with  trucks,  and  a  track 
should  be  laid  so  that  the  tank  can  be 
run  under  the  rolling  barrel  to  receive 
the  prepared  work.  C  is  a  water  tank 
for  storing  the  prepared  castings  after 
rolling,  as  hereafter  described;  D,  E, 
F  and  G  -are  divisions  of  one  common 
tank;  D  is  to  contain  an  alkali  solu- 
tion, and  should  be  provided  with  a 
steam  coil,  as  shown,  to  heat  the  solu- 
tion; E  is  a  compartment  for  contain- 
ing water  for  rinsing;  F  is  to  contain 
FIG.  52-FBONT  ELEVATION  an  add  ^^  .  G  ig  for  ^  muriate 

of  zinc;  H  is  the  roughing  kettle  of  tin;  K  is  the  fiiii- 
ishing  kettle;  L  is  the  kerosene  for  cooling  the  work.  The 
arrangement  of  this  tank  was  explained  in  the  chapter  on 


TINNING  GRAY  IRON  CASTINGS 


131 


general  tinning;  M  is  a  wooden  tank  large  enough  to  ac- 
commodate the  iron  tank  L  arid  allow  it  to  be  surrounded 
with  water;  N  is  a  tank  for  containing  hot  water,  in  which  the 


FIG.  53 — SIDE  ELEVATION  OF  TINNING  FURNACE 

tinned  work  is  dipped  to  remove  any  traces  of  oil  or  acid,  and 
is  provided  with  a  steam  coil,  as  shown;  0  is  a  box  to  contain 
sawdust  for  drying  off  the  work  when  it  conies  from  the  hot  water 


FIG.  54 — PLAN  OF  TINNING  FURNACE  AT  GRATE  LINE 

contained  in  the  tank  N ;  R  R  is  a  drain  for  carrying  off  the  waste 
water,  and  S  S  are  the  tracks  for  moving  the  tanks  B  and  C; 
T  is  a  tank  for  containing  a  solution  of  hydrofluoric  acid,  used 
as  hereafter  described,  and  U  is  a  storage  tank.  It  is  perhaps 


132  GALVANIZING  AND  TINNING 

needless  to  say  that  the  ground  plan  may  he  changed  to  suit  local 
conditions. 

Only  the  most  simple  tools  are  required,  which  may  be  varied 
by  the  ingenuity  of  the  operator  to  suit  existing  conditions  of 
work.  We  give  a  sketch  showing  the  most  common  in  Fig.  25. 


Wa.na.ce  Q.  Imhojfr 

CHAPTER  XVIII 

Preparing  Gray  Iron  Castings  for  Tinning 

IN  PREPARING  gray  iron  castings  to  take  a  coating  of  tin 
there  are  several  essential  things  to  be  taken  into  considera- 
tion; viz.,  the  quality  of  the  iron,  the  form  of  the  castings, 
their  condition  when  they  come  to  the  tinner  anci,  1^  cored,  HEne 
nature  of  the  cores  used. 

TTanl  iron  requires  longer  preparation  than  soft  iron  and  a 
longer  immersion  in  the  molten  tin.  Castings  made  from  patterns 
not  designed  with  a  view  of  avoiding  sharp  angles,  and  in  which 
molding  sand  can  easily  find  lodgment,  are  much  more  difficult 
to  prepare  than  those  made  from  patterns  free  from  such 
hindrances.  It  is,  of  course,  not  always  possible  to  do  away  with 
sharp  angles  in  making  patterns  for  castings  that  are  designed  to 
be  tinned,  but  whenever  possible  they  should  be  avoided  in  the 
interest  of  easy  cleaning  and  perfect  coating  of  the  work. 

Castings  that  have  been  freed  from  sand  by  the  use  of  sulphuric 
acid  require  a  special  preparation  before  they  will  take  a  perfect 
coating  of  tin,  and  the  use  of  this  acid  for  this  purpose  should 
be  avoided  if  possible.  Cored  castings  made  with  cores  in  which 
rosin  has  been  used  must  be  treated  differently  from  those  made 
with  an  oil  or  glue  core.  For  the  intelligent  understanding  of  the 
different  conditions  we  give  the  specific  course  to  be  followed  in 
each  case. 

The  perfect  coating  of  gray  iron  requires  the  use  of  two  tin-. 
ning  kettles,  and  where  castings  are  to  be  tinned  previous  to  elec- 
troplating three  kettles  of  tin  should  lie  used  to  insure  the  smooth- 
est coating  and  the  brightest  luster. 

Removing  Sand  from  the  Castings 

The  first  operation  in  preparing  the  castings  for  tinning  is  to 
free  them  from  sand.  This  is  best  accomplished  by  the  use  of 
the  ordinary  tumbling  barrel^jvhich  gives  the  eastings  a  smooth, 
clean  surface  while  removing  the  sand.  Where  the  castings  are  of 
a  nature  which  prevents  their  perfect  cleaning  by  tumbling,  the 
o  removed  by  a  solution  of  hydrofluoric  acid  and 
138 


134  GALVANIZING  AND  TINNING 

water.  Sulphuric  acid  will  do  the  work,  but  in  a  much  inferior 
manner  and  to  the  detriment  of  the  castings  as  regards  their  easy 
and  perfect  coating  in  the  tin.  The  reason  for  this  is  easily  under- 
stood. Hydrofluoric  acid  acts  directly  on  the  sand,  dissolving  it 
rapidly  without  attacking  the  iron  to  any  great  extent.  The  action 
of  sulphuric  acid  is  just  the  reverse,  the  iron  being  dissolved  on 
the  surface  of  the  casting,  causing  the  sand  to  fall  off,  the  sand 
itself  not  being  affected. 

Freeing  Gray  Iron  Castings  from  Sand  by  Hydrofluoric  Acid 
While  this  operation  is  about  the  same  as  given  for  cleaning 
malleable  iron  by  the  use  of  this  acid,  we  wish  to  impress  the 
operator  with  the  fact  that  in  treating  gray  iron  with  acid  of  any 
kind,  in  preparing  it  for  tinning,  much  more  care  must  be  exer- 
cised in  the  operation  than  with  malleable  iron,  as  the  over- 
pickling  of  gray  iron  leaves  the  surface  soft  and  gunfmyT  m~  wliieH**- 
condition  it  will  not  take  a  coating  of  tin  and  it  is  no  easy 
'matter  to  put  it  in  a  condition  where  it  wiilT 

~~  For  quick  cleaning  of  sandy  castings  by  the  use  of  hydrofluoric 
acid  the  preparation  should  be  1  of  acid  to  20  of  water.  For 
slow  cleaning,  which  is  necessary  on  castings  having  sharp  angles 
into  which  the  molding  sand  has  burned,  use  the  acid  in  the 
proportion  of  1  of  acid  to  30  of  water.  The  castings  may  remain 
in  this  solution  until  the  sand  is  dissolved,  after  which,  provided 
they  have  not  been  made  with  rosin  cores,  they  are  ready  to  be 
place,d  in  the  tumbling  barrel  used  to  prepare  them  for  tinning. 
If  rosin  cores  have  been  used  the  castings  are  to  be  treated  in 
a  special  way,  which  will  be  explained  in  its  turn. 

A  goqd  arrangement  for  cleaning  sandy  castings  with  hydro- 
fluoric acid  is  to  have  two  tanks  (oil  barrels  sawed  in  half  will 
answer),  one  elevated  above  the  other  by  means  of  a  stand  or 
bench,  so  that  the  top  of  the  lower  tank  will  be  3  or  4  inches  below 
the  bottom  of  the  elevated  tank.  Bore  a  hole  in  the  side  of  the 
upper  tank  close  to  the  bottom  and  provide  a  plug.  Place  the 
castings  in  the  upper  tank  and  cover  them  with  the  hydrofluoric 
solution,  which  is  contained  in  the  tank  below.  When  the  cast- 
ings have  been  completely  freed  from  sand  remove  the  plug  and 
allow  the  solution  to  escape  into  the  tank  below,  where  it  remains 
until  required  for  use  again.  No  specific  rules  can  be  given  as 
to  the  time  required  to  clean  castings,  and  it  is  not  necessary,  as 


PREPARING  GRAY  IRON  CASTINGS  FOR  TINNING          135 

an  examination  of  the  work  from  time  to  time  while  under  treat- 
ment will  determine  when  they  are  clean.  Castings  on  which  a 
light  deposit  of  sand  is  attached  may  be  clean  after  15  minutes'  im- 
mersion in  the  solution,  while  castings  having  a  heavy  coating  of 
sand,  or  on  which  the  sand  has  burned,  may  require  3  or  4  hours. 
If  the  nature  of  the  sand  on  the  castings  makes  it  seem  prob- 
able that  they  will  require  a  longer  immersion  in  the  acid,  weaken 
the  solution  by  the  addition  of  water  to  a  point  where  there  can 
be  no  possible  danger  of  the  castings  being  affected  in  the  way 
mentioned  in  the  beginning  of  this  subject. 

Cleaning  Sandy  Castings  with  Sulphuric  Acid 
If  sulphuric  acid  is  used  to  free  the  castings  from  sand,  place 
them  on  an  inclined,  raised,  platform,  which  platform  should  be 
of  a  size  to  accommodate  the  intended  production  and  arranged 
to  allow  the  solution  to  flow  back  into  a  tank  placed  at  the  lowest 
point  to  receive  it.  Make  the  solution  in  the  proportion  of  1  of 
acid  to  6  of  water,  and  keep  the  castings  wet  with  this  solution 
until  the  sand  can  readily  be  removed  by  a  stream  of  water.  Gray 
iron  castings  cleaned  in  this  way  will  have  a  soft,  gummy  surface, 
and  will  not  take  as  perfect  a  coating  of  tin  as  castings  cleaned  by 
dry  tumbling  or  by  the  use  of  hydrofluoric  acid.  They  must  be 
given  a  special  treatment  before  tinning,  which  will  be  described 
in  connection  with  the  treatment  of  castings  made  with  rosin 
cores  and  hard  or  greasy  castings. 

Cleaning  Castings  with  the  Sand  Blast 
In  addition  to  the  methods  already  described  for  preparing 
gray  iron  castings  for  tinning,  the  reader  should  not  lose  sight 
of  the  fact  that  the  sand  blast  is  a  valuable  agent  for  this  pur- 
pose, and  we  strongly  advise  those  who  have  sufficient  work  to 
warrant  the  installation  of  a  sand  blast  plant  to  carefully  inves- 
tigate its  possibilities.  Special  attention  is  given  to  this  subject 
in  Chapter  VI,  pages  51  to  65. 

The  Use  of  a  Hot  Alkali  Bath  in  Certain  Cases 

After  the  castings  have  been  freed  from  sand  in  some  one  of 
the  ways  described,  provided  they  have  not  been  over-pickled,  or 
made  with  rosin  cores,  or  greasy,  and  have  not  been  faced  with 
black  lead  facing,  or  picked  with  sulphuric  acid,  they  are  ready 
for  tumbling  in  the  solution  of  muriatic  acid,  sal  ammoniac  and 


136  GALVANIZING  AND  TINNING 

water.  If  any  of  these  conditions  should  prevail,  the  castings 
must  be  given  a  treatment  in  a  bath  of  hot  caustic  soda  or  soda 
ash. 

If  castings  have  been  over-pickled — that  is,  left  in  the  pickle 
until  the  surface  has  become  covered  with  a  soft,  gummy  sub- 
stance— or  if  rosin  cores  have  been  used  in  making  the  castings 
or  black  lead  facing  used  to  give  a  smooth  surface,  or  if  grease 
or  paint  is  present,  they  must  be  immersed  for  several  minutes 
in  a  boiling  solution  of  caustic  soda  or  soda  ash.  Make  the  solu- 
tion very  strong,  and  see  that  the  strength  is  maintained  by  adding 
fresh  material  as  needed. 

After  this  treatment  the  castings  must  be  thoroughly  washed 
with  clean  water  before  they  are  placed  in  the  rolling  barrel  used 
to  prepare  them  for  tinning.  D  in  Fig.  30  designates  the  tank 
to  be  used  for  the  hot  alkali  solution  and  E,  in  the  same  illus- 
tration, is  the  tank  used  for  rinsing. 

Tumbling 

Special  care  is  required  in  preparing  cast  iron  for  tinning,  in  the 
tumbling  barrel  and  a  very  comprehensive  treatment  of  the  subject 
is  given  in  Chapter  VI,  pages  51  to  65.  This  material  covers  the 
construction,  location,  charging  and  operation  of  the  barrel. 

The  important  point  to  keep  in  mind  in  preparing  cast  iron  for 
tinning  is  that  the  surface  of  the  iron  must  be  made  perfectly 
_clean^  Not  only  free  from  sand  and  rust,  but  from  every  foreign 
substance.  It  may  seem  to  the  reader  that  we  are  dwelling  on 
this  point  unnecessarily,  but  only  by  the  most  careful  attention  to 
the  proper  preparation  of  the  castings,  and  in  the  keeping  of  them 
in  the  same  clean  condition  until  they  receive  the  first  coat  of  tin, 
can  perfectly  satisfactory  work  be  obtained. 

If  the  iron  is  allowed  to  roll  in  the  solution  too  long  a  time 
the  surface  becomes  soft  from  the  action  of  the  acid  and  the  tin 
will  not  take.  The  same  trouble  will  be  experienced  if  the  solu- 
tion in  the  rolling  barrel  is  too  strong,  or  if  the  castings  are 
allowed  to  remain  in  the  solution  too  long  after  they  are  rolled. 

Water  Rolling 

Where  castings  are  tinned  for  the  purpose  of  electroplating 
them,  it  is  desirable,  if  an  extra  smooth  surface  is  desired,  to 
give  them  a  rolling  in  gravel  and  water  in  the  ordinary  wet 


PREPARING  GRAY  IRON  CASTINGS  FOR  TINNING  137 

rolling  barrel,  although  this  treatment  is  not  necessary  in  order  to 
prepare  them  to  take  a  coating  of  tin.  In  treating  castings  in 

this  way  u>e  a  coarse  hard  gravel,  and  some  eastings  may  be 
rolled  20  to  30  hours  to  good  advantage  if  the  barrel  is  properly 
loaded. 


CHAPTER  XIX 

Coating  Gray  Iron  Castings  with  Tin 

THE  tin  in  the  kettles  being  at  the  proper  heat  for  the  work 
in  hand,  as  specified  later  on,  the  operator  takes  a  small 
quantity  of  the  castings  from  the  storage  tank  C,  Fig.  51, 
and  places  them  in  the  wire  basket  designated  A  in  Fig.  25,  tak- 
ing care  to  place  those  having  concave  sides,  holes  or  depres- 
sions so  that  none  of  the  various  solutions,  through  which  they 
are  now  to  pass,  will  be  retained.  The  castings  contained  in  the 
basket  must  now  be  immersed  in  the  solution  of  caustic  soda  or 
potash,  which  is  contained  in  tank  D,  Fig.  51.  This  solution 
must  be  kept  at  the  boiling  point,  and  from  1  to  2  minutes  is 
sifficient  time  to  leave  the  castings  in.  The  best  plan  for  heat- 
ing this  solution  is  to  have  a  steam  coil  in  the  bottom  of  the 
tank,  as  shown  in  the  illustration,  and  to  allow  the  exhaust  steam 
to  pass  into  the  rinsing  tank,  which  is  placed  beside  it,  as  shown 
in  the  ground  plan.  The  rinsing  tank  is  designated  E  in  Fig. 
51.  After  the  basket  of  castings  has  stood  in  the  alkali  bath  con- 
tained in  tank  D  for  the  desired  time  it  is  placed  in  the  rinsing 
tank  E  until  all  traces  of  that  solution  are  removed.  This  will 
take  but  a  fraction  of  a  minute,  provided  a  stream  of  clean  water 
is  kept  flowing  into  the  tank,  as  it  should  be,  In  rinsing  the  cast- 
ings in  tank  E  do  not  allow  them  to  remain  in  the  tank  for  any 
great  length  of  time  if  water  is  flowing  in,  as  iron  will  soon  rust 
in  running  water. 

The  next  move  is  to  immerse  the  basket  of  castings  in  a  very 
weak  solution  of  muriatic  acid  and  water,  1  part  acid  to  40  of 
water.^  The  tank  for  containing  this  solution  is  designated  F  in 
Fig.  51,  and  the  castings  must  not  be  allowed  to  remain  in  it 
more  than  2  or  3  seconds.  The  solution  should  be  made  up  fresh 
after  2  or  3  tons  of  iron  have  passed  through  it. 

Next,  place  the  basket  of  castings  in  the  tank  G,  Fig.  51,  which 
contains  muriate  of  zinc,  to  which  has  been  added  5  pounds  of 
gray  granulated  sal  ammoniac  for  every  gallon  of  the  liquid. 
Muriate  of  zinc  is  made  by  dissolving  zinc  in  muriatic  acid,  allow- 

138 


COATING  GRAY  IRON  CASTINGS  WITH  TIN  139 

ing  the  acid  to  dissolve  all  the  zinc  it  will.  An  earthen  crock 
or  a  cleaned  oil  barrel  can  be  used  to  make  this  cut  acid  in.  This 
solution  should  be  deep  enough  to  cover  the  castings  contained  in 
the  wire  basket  used  for  immersing  them  in  the  roughing  kettle, 
and  should  be  kept  in  good  condition — that  is,  care  should  be 
taken  to  prevent  its  being  weakened  to  any  great  extent  by  pass- 
ing the  solution  in  tank  F  into  it  with  the  work.  The  tank  for 
containing  this  muriate  of  zinc  should  be  lead  lined,  and  an  inner 
lining  of  wood  used  to  protect  the  lead. 

The  basket  of  castings  is  now  ready  to  be  immersed  in  the 
molten  tin  contained  in  the  first,  or  roughing,  kettle,  and  shown 
in  Fig  51  at  H  The  tin  in  this  kettle  should  attain  a  heat  of 
500  degrees  F.,  and  this  heat  should  be  maintained  during  tne 
time  the  kettle  is  in  use. 

Before  immersing  the  castings  in  this  kettle  the  surface  of  the 
tin  should  be  covered  by  a  flux,  made  by  boiling  a  quantity  of 
the  muriate  of  zinc  on  top  of  the  molten  tin,  and  adding  quickly 
to  the  boiling  mass  a  quantity  of  white  granulated  sal  ammoniac. 
The  sal  ammoniac  must  be  added  by  sprinkling  it  on  before  the 
acid  is  evaporated  by  the  heat  of  the  tin  It  will  take  a  little 
time  and  experience  before  the  proper  consistency  of  this  flux  can 
be  attained  T_^°  pr^p°r  making  of  this  flux  is  one  of  the  most 
essential  points  in  the  .successful  coating  of  cast  iron  in  this  first 
kettle  of  tin.  If  the  flux  is  allowed  to  become  hard  and  dry,  as 
it  soon  will  by  continued  use  unless  careful  and  constant  atten- 
tion is  given  to  it,  the  flux  will  adhere  to  the  castings  as  they  pass 
through  it  into  the  tin  below,  and  thereby  prevent  them  from 
coating. 

When  it  is  found  that  the  flux  is  becoming  thick  and  lumpy, 
add  a  sufficient  quantity  of  muriate  of  zinc  and  powdered  sal  am- 
moniac to  cause  the  flux  to  boil  up  to  a  depth  of  £  inch  or  more. 
When  this  result  is  obtained  take  a  perforated  iron  skimmer  and 
carefully  remove  any  hard  lumps  and  congealed  matter  remain- 
ing in  the  flux,  allowing  such  as  readily  pass  through  the  skim- 
mer to  remain  in  the  kettle.  The  purpose  of  this  flux  is  to  pre- 
vent  the  surface  of  the  tin  from  becoming  oxidized  by  exposure 
to  the  air,  and  also  to  prevent  the  hot  metal  from  spattering  and 
burning  the  operator  when  the  wet  castings  come  in  contact  with 
the  tin.  B'-ar  carefully  in  mind  that  this  flux  must  at  all  times 
be  kept  in  a  thm  liquid  condition,  otherwise  the  succeeding  opera- 


140  GALVANIZING  AND  TINNING 

tions  through  which  the  castings  are  to  pass  before  they  are  com- 
pleted will  be  unsuccessful. 

In  forcing  the  castings  into  the  roughing  kettle,  care  should  be 
taken  to  get  them  immersed  as  soon  as  possible.  If  they  are 
allowed  to  float  on  the  surface  of  the  tin  the  muriate  of  zinc, 
with  which  they  are  wet  (for  the  purpose  of  causing  the  tin  to 
adhere),  will  dry  off,  and  the  tin  will  not  adhere  to  the  part  of 
the  casting  thus  exposed  The  castings  must  be  kept  below  the 
surface  of  the  tin  until  they  have  become  as  hot  as  the  tin  itself, 
and  until  the  tin  has  ceased  to  bubble  or  to  be  agitated  by  the 
castings  that  are  immersed.  This  boiling  or  agitation  will  cease 
when  the  air  and  moisture  is  expelled  from  the  iron  and  the  flux, 
that  adhered  to  it  as  it  passed  through,  has  risen  to  the  surface 
of  the  tin. 

The  proper  way  to  immerse  the  work  in  this  first  kettle  of  tin 
is  to  rest  the  handle  of  the  basket  containing  it  on  a  block  of 
iron  placed  on  the  edge  of  the  tin  kettle,  elevating  the  basket  at 
an  angle  that  will  prevent  it  touching  the  molten  tin  until  the 
operator  is  ready  to  have  it.  Cant  the  basket  so  that  one  of  the 
lower  edges  will  enter  the  tin  first;  in  other  words,  do  not  allow 
the  flat  bottom  of  the  basket  to  come  directly  onto  the  surface  of 
the  tin,  as  the  effect  of  having  as  much  wet  metal  as  the  bottom 
of  the  basket  presents  coming  in  contact  with  the  molten  tin  will 
be  an  explosion,  resulting,  perhaps,  in  the  serious  injury  of  the 
operator  or  some  one  standing  near.  When  the  basket  is  in  the 
described  position,  lower  it  carefully  until  1  inch  or  2  inches  of 
the  bottom  and  one  side  is  immersed  in  the  tin,  then  lower  rapidly, 
but  steadily,  until  the  basket  and  its  contents  are  completely 
immersed. 

At  this  point  turn  the  basket  completely  over,  bottom  up,  and, 
using  the  edge  of  the  tin  kettle  as  a  rest  for  the  handle,  lift  the 
basket  from  the  tin  when  it  is  free.  Turn  it  bottom  down  and 
use  it  in  that  position  to  keep  the  castings  it  contained  below  the 
surface  of  the  tin  until  they  reach  the  heat  of  the  metal.  Fill 
the  kettle  with  as  many  castings  as  it  will  hold  and  allow  them 
to  be  completely  immersed.  Several  of  the  wire  baskets  may  be 
employed  to  insure  having  a  batch  always  ready  to  immerse  when 
a  previous  one  has  been  disposed  of. 

It  sometimes  happens  that  the  operator  carelessly  omits  dip- 
ping the  work  in  the  cut  acid  contained  in  tank  G,  Fig.  51;  that 


COATING  GRAY  IRON  CASTINGS  WITH  TIN  141 

is,  he  may  attempt  to  immerse  the  work  in  the  molten  tin  directly 
from  tank  D,  E  or  F.  Such  neglect  is  dangerous  and  likely  to  be 
attended  with  serious  results  to  the  operator,  due  to  spattering  of 
the  hot  metal. 

There  are  many  kinds  of  castings  that  may  be  strung  on  wires 
and  handled  through  the  different  stages  without  the  use  of 
wire  baskets.  When  wires  are  used  the  shape  may  be  varied  to 
suit  conditions.  While  we  show  the  most  common  in  Fig.  25,  the 
ingenuity  of  the  operator  mu.?t  be  employed  in  selecting  and  de- 
vising those  best  adapted  to  his  wants. 

The  kettle  being  filled,  as  described,  the  castings  must  now 
remain  where  they.^j^_for,  ^rorn_5_to  1Q  minnfe^  oj1  .until __they__ 
have  taken   a  perfect  coating  of  tin.     If,  in  this  time,  they  arc 
not  properly  coated,  some  error  has  been  made  in  the  previous 
operations  and  the  work  must  be  re-rolled. 

What  dross  or  slag  forms  in  a  tin  kettle  rises  to  the  surface. 
A  considerable  part  of  this  objectionable  matter  will  be  found  in 
the  first  kettle,  and  must  be  removed  before  the  work  can  be  car- 
ried to  the  finishing  kettle  or  kettles.  To  accomplish  the  removal 
of  this  dross,  or  slag,  floating  on  the  surface  of  the  tin,  use  a  _ 
perforated,  concaved  iron  skimmer.  The  holes  in  the  skimmer 
should  be  large  enough  to  allow  the  clear  tin  to  How  through 
freely,  and  care  should  be  taken  not  to  waste  the  flux  in  skim- 
ming out  the  dross.  If  the  skimmer  is  canted  edgewise  the  dross 
will  adhere  to  the  skimmer,  while  the  flux  and  clear  tin  will  flow 
back  into  the  kettle. 

When  all  the  dross  has  been  removed  from  the  kettle,  grasp 
one  of  the  castings  with  a  pair  of  tongs  and  remove  it  with  a 
quick  motion  from  the  tin.  If  wires  have  been  employed  for 
stringing  the  work,  take  one  or  more  wires  •  and  remove  in  the 
same  way  to  the  next  kettle,  taking  care  that  no  flux  or  dross  is 
carried  along  with  the  work.  The  temperature  of  the  tin  in  the 
first  kettle  is  much  too  high  for  finishing  work,  and  when  the 
castings  taken  from  it  are  exposed  to  the  air  they  will  turn  more 
or  less  yellow,  depending  on  the  heat  of  the  tin.  A  bright  yellow 
or  golden  color  indicates  too  high  a  heat  and  must  be  avoided. 
A  slight  yellowish  tinge  indicates  the  proper  heat. 

The  tin  in  the  second  kettle,  which  is  designated  in  Fig.  51  as 
K,  and  which,  in  most  cases,  is  the  finishing  kettle,  must  be  main- 
tained at  a  temperature  of  about  400  degrees  F.,  and  the  surface 


J 


142  GALVANIZING  AND  TINNING 

must  be  kept  covered  to  the  depth  of  from  £  to  1  inch  with  pure 
beef  tallow.  Palm  oil  may  be  introduced  into  the  tallow  with  good 
results,  using  about  10%  palm  oil.  The  operator  keeps  the  cast- 
ings held  by  the  tongs  or  wires  immersed  in  this  second  kettle  1 
or  2  seconds  and  then,  with  the  tongs  held  in  the  left  hand,  he 
removes  the  piece  from  the  tin.  As  soon  as  the  piece  is  clear  of 
the  tin  the  operator  grasps  it  with  another  pair  of  tongs  held 
in  the  right  hand  and,  after  a  few  rapid  swinging  motions  to  free 
the  article  from  surplus  tin,  plunges  it  into  the  tank  containing 
kerosene  oil.  If  wires  are  being  used  he  swings  the  work  to 
and  fro  rapidly  to  free  it  from  the  surplus  tin,  and  when  plung- 
ing it  into  the  oil  he  must  give  the  work  a  motion  calculated  to 
prevent  the  articles  in  contact  from  adhering  to  each  other. 

The  tank,  which  is  designated  in  Fig.  51  as  L,  should  be  of 
sheet  iron  and  placed  in  the  companion  tank  M  with  the  idea  of 
having  running  water  surrounding  it  to  keep  the  kerosene  from 
becoming  over-heated,  as  it  soon  would  be  from  having  hot  cast- 
ings continually  immersed  in  it.  The  work  must  be  immersed  in 
this  oil  long  enough  to  set  the  tin  and  then  immersed  in  the 
cold  water  contained  in  the  companion  tank  M. 

If  the  tin  in  the  finishing  kettle  is  at  the  right  temperature 
the  work  will  lie  white  and  have  a  nice  lustfr  after  it  is  cooled. 
-fir the  work  is  rough  and  lumpy  it  indicates  that  the  tin  in  the 
"finishing  kettle  was  not  hot  enough  or  that  the  work  was  kepVm 
the  air  too  lorn*  a  time  before  dipping  it  in  the  kerosene.  The 
tin  in  the  finishing  kettle  requires  very  little  lire  to  lie  maintained. 
as  there  will  be  nearly  enough  heat  in  the  castings  brought  from 
the  first  kettle  to  keep  the  tin  in  the  second  at  a  proper  heat.  ^If 
the  vvork  is  yellow  after  cooling  in  the  oil  it  may  indicate  too 
high  a  heat  in  the  finishing  kettle,  or  it  may  indicate  that  the 
casting  was  not  kept  in  the  finishing  kettle  long  enough  to  hring 
the 'heat  thai  the  casting  attaine^  jr  fV>0  flT~pf  i-pff.1p  fjfflyn  to  a 
point  where  the  tin  would  not  turn  Yellow. 

Work  can  be  taken  from  the  finishing  kettle  smoothly  and 
brightly  coated  even  when  the  temperature  of  that  kettle  is  so 
low  that  if  a  piece  of  cold  iron  be  put  into  it  the  tin  would  adhere 
to  the  iron  in  a  thick  mass.  The  heat  the  castings  attain  in 
the  first  kettle  makes  it  possible  to  run  the  finishing  kettle  at  a 
very  low  temperature,  and  it  is  advisable  to  do  so  on  very  heavv 
eastings.  Light  eastings  require  that  a  much  higher  heat  be 


COATIXU  (iRAY  IRON  CASTINGS  WITH  TIN  143 

maintained  in  the  finishing  kettle  than  is  necessary  for  heavy 
Castings.  _  The  reason  is  apparent:  All  castings  must  be  exposed 
to  the  air  a  few  seconds  while  the  operator  is  switching  off  the 
surplus  tin.  If  the  castings  are  light  and  the  tin  is  cold  they 
will  not  hold  the  heat  long  enough  to  allow  the  surplus  tin  to  be 
shaken  off  without  leaving  rough,  ragged  edges. 

A  great  deal  of  ingenuity  can  be  displayed  by  the  operator  in 
the  handling  of  castings  of  various  shapes  in  such  a  way  that 
no  lumps  or  bunches  of  tin  will  remain  on  the  work  after  it  is 
cooled.  For  example,  care  should  be  used  to  ascertain  what  part 
of  a  casting  is  best  adapted  to  be  taken  hold  of  by  the  cooling 
tongs  without  leaving  marks  of  the  tongs  after  the  article  is 
cooled.  The  tongs  used  for  cooling  should  never  be  put  into  the 
tin  kettle,  as  the  heat  of  the  casting  would  cause  it  to  adhere 
to  the  tongs  if  they  were  tinned.  After  shaking  off  the  surplus 
tin,  change  the  position  of  the  casting  so  that  the  drop  of  tin, 
which  will  naturally  collect  at  the  lowest  point,  will  flow  back 
into  the  coating  on  the  casting,  and  dip  it  in  the  oil  at  once  when 
this  is  accomplished. 

A  "switching  box"  should  be  employed,  when  "strung"  work  is 
being  handled,  to  catch  the  tin  that  is  thrown  from  the  work 
in  the  operation  of  "switching"  it  to  throw  off  the  surplus  metal. 
Tliis  box  is  a  very  simple  affair.  Its  position,  when  in  use,  is 
designated  D,  Fig.  23.  sCoverthe  interior  of  the  box  with  heavy 
paper,  as  the  hot  tin  will  stick  to  the  wood  unless  paper  is  used. 
The  tin  thus  collected  may  be  thrown  into  the  kettle  with  the 
paper  when  the  tin  is  needed  for  use. 

When  the  castings  have  been  cooled,  as  already  described,  they 
should  be  immersed  in  a  tank  of  boiling  water  to  free  them  from 
oil  and  also  to  remove  any  trace  of  acid  that  may  be  on  them. 
This  final  rinsing  tank  is  designated  N"  in  Fig.  51.  The  water 
must  be  kept  clean  and  at  the  boiling  point  at  all  times  when 
in  use.  An  ordinary  foundry  riddle,  with  upright  handles  long 
enough  to  allow  the  operator  to  set  the  riddle  containing  the  work 
to  be  rinsed  into  the  tank  without  scalding  his  hands,  may  be 
employed. 

Xhe  castings  should  be  dried  off  in  clean  dry  sawdust,  and  that, 
niiiild  from  pine  or  some1  soft  wood  is  liftsj^^snaTf!  wood  sawdust 


will  scratch  the  tinned  surface.    The  drying  box  is  shown  at  0  in 

Fig.  51. 


144  GALVANIZING  AND  TINNING 

When  three  kettles  of  tin  are  employed,  as  they  may  lie  to  good 
advantage  in  tinning  work  that  is  designed  to  be  plated,  the 
second  kettle  must  be  run  at  a  temperature  of  450  degrees  F.  The 
surface  of  the  tin  in  this  kettle  must  be  kept  covered  with  an 
acid  and  sal  ammoniac  flux  the  same  as  the  first  kettle.  The 
castings  in  the  first  kettle  are  passed  in  quantities  to  the  second 
kettle,  there  to  remain  until  the  first  kettle  is  refilled.  As  when 
using  two  kettles,  care  must  be  taken  to  prevent  any  of  the  slag 
or  flux  that  accumulates  on  the  first  kettle  from  passing  with 
the  work  into  the  second  kettle,  and  the  tin  in  the  second  kettle 
must  be  kept  free  from  slag. 

The  tin  in  the  third  or  finishing  kettle  should^  be  maintained 
ot  a  temperature  of  100  decrees  F..  and  the  depth  of  the  tallow 

1  «_  J  i 

iiJi'rea!Jed'  io  3  or  4jnches. 

If  three  kettles  are  employed  they  should  lie  square  or 
round,  and  arranged  to  fire  from  one  side  instead  of  from  the 
ends. 

As  it  is  almost  impossible  to  satisfactorily  tin  castings  which 
have  been  imperfectly  coated  at  the  first  attempt,  the  operator 
should  give  careful  attention  to  details. 

It  is  comparatively  easy,  with  practice,  to  keep  the  tin  at  a 
proper  heat,  but  the  beginner  will  find  more  difficulty  in  doing 
this  than  any  other  one  thing  in  the  entire  operation.  That  the 
proper  heat  be  maintained  is  very  essential,  for  if  it  is  not  all 
previous  care  in  preparing  the  work  will  have  been  in  vain.  If 
too  hot  the  flux  on  the  roughing  kettle  will  evaporate  or  burn  off, 
and  the  tin  will  not  coat  the  iron.  If  too  high  a  heat  is  reached 
on  the  fini.-hing  kettle  the  tallow  will  be  set  on  fire.  As  .a  help 
to  the  "novice  and,  in  fact,  to  the  experienced  man,  we  recommend 
the  Tiaft  nf  pvrojnpf.ers ;  one  for  each  kettle.  The  expense  of  pro- 
viding them  is  not  to  be  considered  in  comparison  with  the  ad- 
vantages obtained  by  their  use. 

The  kettles  for  containing  the  tin  usually  are  made  of  cast 
iron,  although  lire  box  steel  is  often  employed  to  make  oblong 
kettles. 

A  floor  space  of  20  x  40  feet  will  accommodate  a  tinning  plant 
having  two  rolling  barrels.  If  possible,  the  plant  should  be  lo- 
cated handy  to  power  and  with  a  view  to  obtaining  easy  and  per- 
fect drainage.  If  necessity  compels  locating  the  plant  in  a  fac- 
tory building  above  the  ground  floor,  as  is  sometimes  the  case,  the 


COATING  GRAY  IRON  CASTINGS  WITH  TIN  145 

floor  of  the  tinning  and  rolling  rooms  must  be  so  constructed  that 
leakage  into  the  room  or  rooms  below  will  be  impossible. 

The  dross  or  slag  formed  in  the  kettles  should  be  stored  away 
until  a  sufficient  amount  has  accumulated  to  make  profitable  the 
remelting  of  it  to  reclaim  what  pure  tin  is  in  it.  For  the  pur- 
pose of  remelting  this  dross  the  pure  tin  can  be  removed  from 
the  kettle  H,  Fig.  51,  and  the  dross  melted  up  in  it.  When  the 
entire  mass  is  in  a  molten  state,  and  at  a  temperature  of  about 
550  degrees  F.,  bail  off  the  good  tin  into  cast  iron  pans  provided 
for  the  purpose,  and  the  dross  which  remains  into  separate  pans. 
This  tin  dross  has  a  market  value  of  from  40  to  50%  of  the 
price  of  pig  tin. 

With  the  addition  of  tanks  for  containing  cleaning  acids,  a  plant 
built  to  tin  cast  iron  is  adapted  to  all  descriptions  of  tinning, 
except  re-tinning  of  tinware  and  the  tinning  of  sheets. 


CHAPTER  XX 
Cleaning  Old  Galvanized  and  Tinned  Work 

GALVANIZED  material  becomes  dark  or  discolored  from 
age  or  exposure  and  from  various  other  causes.  Gal- 
vanized sheet  iron  is  often  found  to  be  covered  with  a 
white  deposit,  which  discolors  them  even  when  the  stock  has  been 
kept  under  cover,  and  it  is  almost  sure  to  be  found  if  it  has 
been  subjected  to  changes  of  temperature  which  have  caused  mois- 
ture to  gather  on  the  sheets.  On  galvanized  castings  the  discolora- 
tion is  seen  in  the  form  of  a  white  powder  which  forms  on  their 
surface,  or,  if  they  have  been  stored  in  a  room  not  subjected  to 
marked  variations  of  temperature,  their  surface  simply  turns 
dark. 

While  it  is  practically  impossible  to  prevent  this  discoloration, 
and  while  it  is  not  particularly  detrimental  to  the  wearing  qual- 
ities of  the  coating,  it  is  often  detrimental  to  the  sale  of  the  mate- 
rial, as  few  care  to  buy  goods  that  have  a  "shop-worn"  appearance. 
The  appearance  of  discolored  material  may  be  materially  improved, 
however,  and  sometimes  made  to  look  like  new,  by  dipping  it  in 
a  cold  solution  of  one  part  sulphuric  acid  to  ten  parts  water.  The 
material  should  not  be  left  in  the  acid  dip  more  than  two  minutes 
at  the  most,  and  as  much  less  as  possible,  and  accomplish  the 
desired  result.  Neither  should  the  material  be  subjected  to  fre- 
quent dippings,  as  it  will  become  permanently  stained  by  so 
doing.  As  soon  as  the  material  has  been  removed  from  the  acid 
solution,  it  should  be  immediately  rinsed  thoroughly  in  clean, 
cold  water,  after  which  it  should  be  immersed  in  a  bath  of  boil- 
ing hot  water,  and  carefully  dried  off  in  dry  sawdust. 

Cleaning  Old  Tinned  Work 

Tinned  work  that  has  been  subjected  to  considerable  handling, 
or  that  has  been  machined,  will  invariably  lose  its  luster.  While 
the  original  luster  cannot  be  completely  restored,  the  appearance 
can  be  improved  by  dipping  the  material  in  a  hot  solution  of  sal- 
soda.  Make  the  solution  rather  weak;  a  pound  of  sal-soda  to  a 
gallon  of  water  will  usually  be  found  strong  enough  for  ordinary 
146 


CLEANING  OLD  GALVANIZED  AND  TINNED  WORK          147 

purposes,  and  a  weaker  solution  should  be  used  if  it  will  accom- 
plish the  desired  result.  As  soon  as  the  work  is  removed  from 
the  sal-soda  solution  it  should  be  carefully  and  thoroughly  rinsed 
in  clean,  cold  water,  and  then  immersed  in  clean,  boiling  water, 
after  which  it  should  be  dried  off  and  rubbed  in  dry  pine  saw- 
dust, to  which  a  little  flour  has  been  added.  If  dry  sawdust  is 
not  available  ordinary  bran  will  answer  the  purpose  very  well, 
provided  all  moisture  on  the  work  has  been  allowed  to  evaporate 
before  the  bran  is  used. 


CHAPTER  XXI 

Electro-Galvanizing  Plant  and  Equipment 

THE  art  of  electro-galvanizing  and  its  industry  is  not  the 
result  of  an  invention,  but  was  simply  created  within  the  last 
twenty  years  by  force  of  necessity  in  protecting,  such  articles 
like  springs,  small  wire  netting,  screws,  bolts,  nuts,  etc.,  which 
could  not  up  to  that  day  be  satisfactorily  galvanized  by  the  hot 
process,  and  this  shows  clearly  that  the  creation  of  the  electro- 
galvanizing  industry  was  not  a  matter  of  cost. 

The  cold  galvanizing  has  its  advantages,  being  suitable  for  treat- 
ing a  large  number  of  different  articles,  especially  goods  that  have 
been  hardened  and  tempered  and  all  kinds  of  machine  parts  with 
perforations  and  threads ;  also  in  the  continuous  processes  for  band 
iron,  wire- and  the  galvanizing  of  small  articles,  such  as  tacks,  nails, 
etc.,  in  bulk  form. 

The  hot  galvanizing  cannot  compete  in  the  satisfactory  produc- 
tion of  these  articles,  and,  on  the  contrary,  the  electro-galvanizing 
never  will  compete  with  the  hot  galvanizing  on  such  articles  as 
tanks,  boilers,  architectural  iron  and  building  material,  etc. 

One  of  the  earliest  records  of  electro-galvanizing  is  an  English 
patent  taken  out  by  Charles  Cleophas  Person,  on  April  27,  1854, 
and  reads  as  follows: 

Coating  with  Zinc  by  Galvanization. 

"The  zincing  is  effected  by  electro-deposition  from  a  bath  con- 
taining salts  of  zinc  and  alumina.  The  solution  may  be  prepared 
liv  di>-ol\  iim'  precipitated  alumina  in  a  solution  of  sulphate1  of 
zinc,  but  the  inventor  prefers  to  dissolve  oxide  of  zinc  in  a  solu- 
tion of  crystalized  alum.  The  zinc  may  be  deposited  from  such 
a  solution  on  all  metals,  viz. :  iron,  copper,  platine,  etc.,  and  the 
adhesion  is  complete :  if  care  is  taken  previously  to  make  the  sur- 
face of  the  article  bright." 

It  is  only  within  the  past  decade  that  any  marked  advance  in 
the  commercial  use  of  electro-deposited  zinc  has  been  noted,  and 
it  is  in  the  United  States  that  the  deposition  of  this  metal,  by 
means  of  a  low-tension  current,  has  reached  its  highest  commercial 
development.  While  the  knowledge  that  zinc  could  be  readily 
148 


•  Imhoff 


ELECTRO-GALVANIZING   PLANT   AND    EQUIPMENT         149 

deposited  has  existed  for  a  long  number  of  years,  the  process  was 
never  taken  up  in  a  practical  commercial  way  until  about  1900. 
At  that  time  attention  was  directed  to  the  subject  through  experi- 
ments made  by  the  governments  of  England,  Germany  and  the 
United  States,  which  demonstrated  the  efficiency  of  the  electro 
deposit  for  certain  classes  of  work.  In  line  with  the  experiments 
which  had  been  made,  the  United  States  Government  established 
tests  and  installed  small  electro-galvanizing  plants  at  various 
arsenals  and  shipyards  throughout  the  country.  Manufacturers 
of  electro-plating  materials  availed  themselves  of  the  information 
brought  to  their  attention,  and  during  the  past  ten  to  twelve 
years  the  growth  of  this  industry  has  been  rapid  and  electro 
zincing  or  galvanizing  is  now  being  applied  to  many  iron  and 
steel  articles  which  could  not  as  readily  be  treated  in  any  other 
way. 

Equipment  for  Electro-Galvanizing  Plant 
An  electro-galvanizing  plant  may  be  subdivided  into  two  im- 
portant departments — the  cleaning  department  and  the  galvaniz- 
ing department  proper.     In  the  cleaning  department  the  equip- 
ment consists  of: 

1.  Suitable  tanks, 

a.  For  sulphuric  or  hydrofluoric  pickle, 

b.  For  hot  potash, 

c.  For   electro-cleaning. 

d.  For  washing  and  scrubbing. 

2.  Tumbling  barrels  or  sand  blasting  apparatus  for  cleaning 

small  material. 

The  galvanizing  equipment  comprises: 

1.  Suitable  tanks  or  automatic  devices,  including  rinsing  and 

drying  apparatus. 

2.  Necessary  galvanizing  solution. 

3.  Copper  conductors. 

4.  Anodes. 

5.  Low-voltage  generator. 

6.  Switchboard  consisting  of  voltmeter,  ammeter  and  rheostat. 

7.  Hot-water  tank. 

This   is  the  complete  unit  for  a  galvanizing  plant  with  still 
tanks,  and  such  equipment  can  be  found  in  the  plants  of  large 


150 


GALVANIZING  AND  TINNING 


metal  manufacturers  and  makers  of  specialties  throughout  the 
country.  Such  a  plant  does  not  require  any  further  explanation. 
A  rough  layout  is  shown  in  Fig.  55. 

Galvanizing  is  accomplished  as  an  accessory  to  other  electro- 
plating activities  or  whole  plants  are  devoted  to  galvanizing  ex- 
clusively. Illustrations  of  the  latter  type  are  shown  in  Figs.  56  and 


p_  

I 

^ 

^ 

- 

^ 

D,.                  Hot  Water  Rinse  Tank               3$              ^  f 

b 

Over  f  Ion      .:Qa!vo^i2!'-.oTar,k                        ^=\  Generator 

^ 

cj 

'•Anode  Rods       ^'-  ttbrkRods                j!g?T                         qj 

c- 

§1.                   Scouring  Tank                      4                        Switchboard 

1 

'•Overflew 

1 

Dm                    13 

1 

^ 

|]                            Potash  Tank                       "jj1 

^ 

— 

1 

FIG.  55.    FLOOR  PLAX  OF  ELECTRO-GALVAXIZIXG  PLANT 


57.  F.ig.  56  shows  one  of  the  most  up-to-date  electro-galvanizing 
departments  in  the  world,  possessing  perfect  light  and  ventilation 
and  ample  room  for  the  operators  to  discharge  their  duties.  The 
plant  shown  is  that  of  the  Spirella  Company,  Niagara  Falls,  N.  Y., 
and  is  devoted  to  the  protection  of  the  wires  of  the  Spirella  (V.-sct 
products.  Fig.  57  shows  a  remarkable  electrical  installation,  with 
22  units  supplying  the  current  for  the  tanks  shown  in  Fiu\  '><>. 
At  no  point  is  the  lead  from  the  generator  to  the  tank  longer  than' 
10  feet. 

A  special  feature  in  this  plant  is  the  covering  of  the  cyanide 
tanks  with  sliding  hoods,  as  shown  on  the  right  in  the  foreground 
of  Fig.  56.  The  fumes  from  these  tanks  arc  taken  away  from 
under  the  hood  by  an  exhaust  blower. 


ELECTRO-GALVANIZING   PLANT    AND    EQUIPMENT          151 


152 


GALVANIZING  AND  TINNING 


ELECTRO-GALVANIZING   PLANT   AND   EQUIPMENT         153 
Mechanical  Galvanizing  and  Patented  Devices 

The  foregoing  paragraphs  have  dealt  in  general  with  electro- 
galvanizing,  and.  as  the  mechanical  electro-galvanizing,  in  other 
words,  the  zinc  deposition  in  bulk  quantities,  has  so  much  merit, 
it  is  worthy  of  special  mention.  The  increasing  use  of  mechanical 
devices  for  electro-deposition  affords  ample  reason  for  an  extended 
study  of  this  juncture  of  the  principles  involved. 

In  the  mechanical  electrical  deposition  of  zinc,  there  is  a  higher 
voltage  and  amperage  used,  and  through  this  in  a  shorter  length 
of  time  more  zinc  is  deposited  than  in  still  open  tanks. 

Still  open  tanks  can  also  be  made  partly  mechanical  by  agitating 
either  the  electrolyte  or  the  goods  to  be  plated.  Some  firms  make 
it  a  practice  to  move  the  bus  bar  either  horizontally  or  perpendicu- 
larly, or  the  electrolyte  is  agitated  by  blowing  air  through  per- 
forated lead  or  rubber  tubes  from  the  bottom  of  the  tanks,  or  by 
agitating  the  solution  through  a  floating-tank  system  or  by  the 
means  of  a  propeller. 

The  above  refers  to  all  kinds  of  articles,  especially  such  work 
which  cannot  be  successfully  plated  in  tumbling  machinery  and 
which  has  to  be  specially  suspended  on  wires,  hooks  or  racks.  Also 
for  this  class  of  work  various  kinds  of  new  machines  and  devices 
have  been  adopted  to  reduce  the  labor  cost  and  shorten  the  time 
of  plating. 

The  Miller  Chain  Conveyer  Machine 

Illustration  58  shows  such  an  apparatus,  patented  by  C.  G. 
Miller,  of  the  Meaker  Company  of  Chicago.  This  machine  carries 
the  goods  by  means  of  a  chain  conveyer  through  the  electrolyte. 
The  chain  conveyer  is  adjusted  in  a  perpendicular  position  and  as 
soon  as  one  article  is  ready  and  thoroughly  plated  another  one  is 
suspended  on  the  same  hook,  making  the  process  a  continuous  one. 

A  indicates  a  tank  conveniently  constructed  of  wood,  though, 
obviously,  it  may  be  lined  with  anv  suitable  material.  As  shown, 
at  the  rear  or  discharge  end  of  said  tank  is  provided  an  upright 
frame  composed  of  posts  a — a',  two  on  each  side,  and  which  may 
be  transversely  connected  in  any  suitable  manner  to  afford  rigidity 
and  strength,  and  journaled  upon  the  uprights  a',  which  are  at 
the  rear  end  of  the  tank,  is  a  shaft  B,  provided  on  its  outer  end 
with  a  worm  gear  b,  adapted  to  be  driven  by  means  of  a  worm 


164 


GALVANIZING  AND  TINNING 


ft1,  on  a  shaft  b2,  provided  with  tight  and  loose-belt  pulleys  I* — b4, 
as  is  usual. 

Journaled  upon  a  standard  C,  at  the  forward  end  of  the  tank, 
is  a  transverse  shaft  C1,  provided  centrally  with  a  sprocket  wheel 
C  thereon.  Journaled  on  adjustable  pulley  blocks  D,  of  any  suitable 
kind,  secured  on  the  rear  end  of  the  tank  on  each  side  thereof  is 
a  shaft  D1,  corresponding  with  the  shaft  C1,  and  parallel  thereto 


FIG.  58.   VERTICAL  SECTION  OF  THE  MILLER  CHAIN  CONVEYER  MACHINE 


and  provided  with  a  sprocket  d  centrally  thereon  and  in  alignment 
with  the  sprocket  wheel  c  on  the  shaft  C1  A  corresponding  sprocket 
wheel  &•"'  is  provided  on  the  shaft  B,  above  the  shaft  I)1,  and  trained 
about  said  sprocket  wheels  is  a  sprocket  or  link-belt  chain  E,  of 
any  suitable  kind  or  construction,  adapted  to  be  run  on  said 
sprocket  wheels. 

As  shown,  the  diameter  of  the  sprocket  wheels  c — d  is  such  that 
the  lower  run  of  the  sprocket  chain  E  is  parallel  with  the  top  of 
the  tank,  and,  of  course,  with  the  electrolyte  in  the  tank,  and 
secured  transversely  on  said  chain  at  short  intervals  apart  are  metal- 
lic bars  e.  which  are  engaged  to  the  appropriate  links  of  said  chain 
near  the  middle  of  each  bar.  Engaged  near  each  end  of  each  of 


ELECTRO-GALVANIZING   PLANT    AND    EQUIPMENT          155 

said  bars  is  a  downwardly  directed  hooked  wire  or  rod  e1,  the  lower 
end  of  which  is  directed  laterally  and  outwardly  toward  the  wall 
of  the  tank,  and  serve  as  hooks  to  support  the  articles  to  be 
plated  or  coated. 

Extending  longitudinally  the  tank  near  each  of  the  side  walls 
and  at  the  middle  of  the  same  are  conductors  / — fl — f~,  which, 
as  shown,  are  round  metallic  rods  connected  with  one  of  the 
leads  f,  from  the  gejierator  F,  on  which  are  suspended  the  anodes 
F1,  which  hang  downwardly  in  the  electrolyte  in  parallel  relation 
with  each  other  and,  of  course,,  may  be  of  any  desired  number, 
and  afford  a  sufficient  surface  for  the  purpose  required.  Said  con- 
ductors are  connected  by  a  cable  /*  with  each  other  at  one  end 
of  the  tank.  As  shown,  the  central,  parallel  bus  bars  f5  are  pro- 
vided on  each  side  the  central  conductor  F1,  and,  as  shown,  are  flat 
bars  of  metal,  which  are  supported  upon  the  top  of  the  tank  and 
projecting  above  the  same,  and  on  which  the  flat  bars  e  on  the 
chain  slide,  and  which  thus  serve  to  support  the  lower  run  of  the 
chain  and  its  load  during  the  plating  operation.  Said  bus  bars 
are  connected  with  the  other  lead  /6  of  the  generator. 

As  shown,  the  shaft  D1,  with  its  sprocket  wheel  d  thereon,  is 
arranged  forwardly  of  the  upper  shaft  B,  and  its  sprocket  wheel, 
thus  inclining  the  upward  run  of  the  chain  outwardly  over  the 
discharge  end  of  the  tank  and,  as  shown,  an  inclined  chute  board 
G,  is  supported  upon  suitable  brackets  on  the  discharge  end  of  the 
tank,  and  its  upper  end  projects  to  near  the  extended  ends  of 
the  hooks  e1,  as  they  rise  from  the  electrolyte,  and  is  adapted  to 
receive  the  articles  discharged  from  said  hooks  to  direct  the  same 
from  the  tank. 

Means  are  provided  for  jarring  the  chain  to  shake  the  articles 
more  or  less  during  the  plating  or  coating  operation,  and  also  to 
remove  the  coated  articles  from  the  hooks.  For  this  purpose,  as 
shown,  a  short  shaft  is  journaled  in  suitable  bearings  on  the 
inner  face  of  each  of  the  uprights  a1  and  the  ends  li — -h1  of  which 
are  directed  oppositely  to  provide  arms.  The  arm  h  is  curved  to 
provide  a  cam,  as  shown  more  clearly  in  Fig.  58,  and  is  adapted  to 
be  engaged  by  the  end  of  each  bar  e,  to  adjust  the  other  arm  h1, 
to  engage  within  the  hook  e1.  Said  arm  h1  is  provided  with  a 
hooked  end  h2,  and  a  spring  hs  is  secured  at  its  ends  to  the  arm 
and  bar  and  acts  to  throw  the  hook  h2  outwardly  when  the  bar  e 
passes  the  cam  li,  thereby  removing  the  articles  from  the  hooks  e1. 


156  GALVANIZING  AND  TINNING 

Operation  of  the  Miller  Machine 

The  operation  is  as  follows :  An  operator  stands  at  the  receiving 
end  Y  of  the  tank  and,  as  the  chain  travels  downwardly  toward 
the  tank  the  current  passes  therethrough  into  the  hus  oars,  thus 
hooks.  This  is,  of  course,  easily  accomplished  if  the  articles  are 
apertured.  If  not,  wire  loops  may  be  provided  whereby  the  articlo 
may  be  engaged  upon  the  hook.  The  chain  is  thus  loaded  progres- 
sively, and  as  the  articles  are  submerged  in  the  electrolyte  within 
the  tank  the  current  passes  there  through  into  the  bus  bars,  thus 
completing  the  circuit.  Obviously,  a  very  large  surface  of  the 
metal  to  be  plated  is  exposed  between  the  anodes  supported  ver- 
tically in  the  tank,  and  as  the  articles  to  be  plated  travel  longitu- 
dinally in  the  tank  between  the  same  the  thickness  of  the  coating 
may  be  regulated  by  the  rate  of  travel  and,  of  course,  the  current. 
Having  passed  through  the  tank,  said  articles  are  raised  from  the 
electrolyte  upon  the  upward  run  of  the  chain  and  as  the  same 
approach  the  hooked  jar  arms  // — //.l  these,  as  .the  successive  bars  e 
engage  the  arm  li,  the  arms  hl  swing  inwardly,  after  which  the 
springs  retract  the  arms  hl  for  their  hooked  ends  to  remove  the 
articles  from  the  carrying  hooks,  adapting  the  articles  to  fall  upon 
the  chute  G.  Owing  to  the  quick  retraction  caused  by  the  spring, 
the  arm  h  of  the  jar  mechanism  is  thrown  inwardly  to  engage  the 
succeeding  bar  e,  which  jars  the  supporting  mechanism  and  par- 
ticularly the  lower  run  of  the  chain  gently,  thus  tending  to  con- 
stantly shift  the  contact  surface  on  the  hook  of  the  article  being 
coated.  In  this  manner,  uniformity  of  the  coating  is  assured. 

In  use,  the  outer  end  of  the  supporting  hook  becomes  slightly 
enlarged  by  the  deposition  thereon  of  the  plating  metal.  This  as- 
sists iff  holding  the  articles  (while  coating)  on  said  hooks,  and,  in 
consequence,  there  is  little  or  no  tendency  of  the  same  to  fall  there- 
from to  the  bottom  of  the  tank. 

Of  course,  other  means  may  be  provided  for  releasing  the  plated 
or  coated  articles  from  the  supporting  hooks,  the  jar  arms,  how- 
ever, acting  simultaneously  and  oppositely,  are  very  effective  and 
are  automatic  in  operation. 

Obviously,  the  lower  run  of  the  chain  is  at  all  times  supported 
in  horizontal  position  whatsoever  the  load  thereon,  by  means  of  the 
bus  bars.  If  the  chain  should  at  any  time  become  slack,  the  ad- 
justment may  be  quickly  made  by  means  of  the  adjustable  bearings 
D  for  the  shaft  D1. 


ELECTRO  GALVANIZING    PLANT    AND    EQUIPMENT          157 


158  GALVANIZING  AND  TINNING 

Daniels  Screw  Conveyer  Machine 

Figs.  59,  60  and  61  show  a  similar  construction  by  which  the 
goods  should  be  first  suspended  on  wires,  hooks  or  racks  and  then 


FIG.  60.   Top  PLAN  VIEW  OF  DANIELS  SCREW  CONVEYER  MACHINE 


FIG.  61.    SIDE  ELEVATION  or  DANIELS  SCREW  CONVEYER  MACHINE 


hung  on  a  screw  conveyer,  fixed  in  a  horizontal  position  within  the 
tank  above  the  solution.  This  device  has  been  patented  by  the 
Hanson  &  Van  Winkle  Company  of  Newark,  N.  J. 


ELECTRO-GALVANIZING   PLANT    AND   EQUIPMENT          159 

In  apparatus  herein  shown  10  indicates  the  vat  for  containing 
the  bath,  and  1.1  the  longitudinal  anode  rods  inter-connected  by 
transverse  conductors  12  and  13.  In  the  present  embodiment  of 
the  invention  3  anode  rods  11,  comprising  two  outer  and  one  inter- 
mediate, are  shown.  The  anodes  14  are  hung  on  the  anode  rods  11, 
thereby  subdividing  the  entire  bath  into  two  longitudinally  ex- 
tending lanes  or  spaces,  through  which  successively  it  is  de- 
signed to  convey  the  articles  to  be  plated.  The  number  of  lanes 
or  spaces  thus  formed  may  of  course  be  varied  to  suit  require- 
ments, by  corresponding  variations  in  the  construction  of  the 
apparatus,  but  the  construction  and  arrangement  herein  shown 
will  be  sufficient  to  illustrate  the  invention. 

For  conveying  the  articles  through  the  spaces  to  either  side 
of  the  inner  line  of  anode  rods  conveyer  screws  15  are  provided. 
These  extend  longitudinally  of  the  vat  and  are  disposed  above  the 
level  of  the  bath,  one  on  either  side  of  the  intermediate  line  of 
anode  plates.  The  conveyer  screws  15  may  be  constructed  in  any 
desired  manner,  but  as  shown  herein  they  are  constructed  of 
rods  or  shafts,  on  which  are  disposed  conveyer  coils.  The  con- 
veyer screws  are  journaled  at  one  end  in  suitable  bearings  16,  and 
at  the  other  end  on  a  stationary  curved  rod  17,  as  will  be  clearly 
shown.  Intermediate  of  their  two  ends  the  rods  are  supported  at 
suitable  intervals  by  the  intermediate  supports  or  bearings  18, 
which  as  illustrated  in  Figs.  60  and  61  are  bifurcated  to  permit 
the  passage  of  the  cathode  hangers  19,  as  clearly  shown. 

To  drive  the  two  conveyer  screws  in  opposite  directions  power,  is 
applied  to  belt  pulley  20  fixed  on  shaft  21  suitably  journaled  in 
bearings  22  and  carrying  worm  sections  23  and  24  of  opposite 
pitch,  which  mesh  with  worm  gears  25  and  26,  respectively,  of 
the  two  conveyer  screws.  A  worm  section  27  is  also  provided  on 
shaft  21  which  operates  a  worm  gear  28  fixed  on  longitudinal 
shaft  29  journaled  in  bearing  30.  The  other  end  of  shaft  29 
carries  a  bevel  gear  31,  which  meshes  with  the  bevel  bear  32 
fixed  on  a  vertical  shaft  33,  which  is  journaled. in  a  bearing  3-1 
suitably  mounted  on  the  framework  of  the  apparatus.  Vertical 
shaft  33  has  secured  to  it,  as  illustrated  more  clearly  in  Fig.  61, 
a  transfer  disk  or  wheel  35,  which  runs  on  roller  bearings  3i> 
mounted  in  a  supporting  arm  37  of  the  framework.  The  sup- 
porting arm  37  provides  a  bearing  or  guide  for  the  lower  end  of 


160  GALVANIZING  AND  TINNING 

vertical  shaft  33  as  shown.  The  transfer  disk  or  wheel  35  is 
herein  shown  as  having  its  periphery  formed  with  an  annular  con- 
cave surface,  conforming  in  radius  with  the  stationary  curved 
rod  17  above  referred  to,  whereby  the  curved  rod  receives  support. 
The  curved  rod  serves  as  a  transfer  rod  or  support  while  the 
cathode  hangers  are  being  transferred  from  one  conveyer  screw 
to  another,  as  will  be  shown.  The  two  ends  of  the  transfer  rod 
thus  constituted,  are  reduced  and  provided  with  annular  peripheral 
grooves  38,  forming  ball  races  for  ball  bearings  39,  and  a  pin  race 
for  the  key  pin  40.  The  adjacent  ends  of  the  conveyer  screws  15 
are  bored  to  fit  over  the  reduced  ends  of  the  transfer  rod  17, 
as  clearly  shown  in  Fig.  61,  so  as  to  bear  on  the  ball  bearings  39. 
The  key  pin  40  above  referred  to  is  inserted  through  a  perforation 
near  the  end  of  the  conveyer  screw,  whereby  the  transfer  rod  is 
retained  in  position  upon  the  transfer  disk  35. 

Transfer  disk  35  carries  a  series  of  radial  fingers  41  which 
project  outwardly  from  its  periphery  in  a  plane  beneath  the  plane 
of  the  coils  of  the  conveyer  screws,  which  coils  terminate  within 
the  vertical  circumferential  plane  of  fingers  41,  but  not  in  the 
path  of  the  fingers. 

Operation  of  Daniel's  Screw  Conveyer  Machine 

The  operation  of  the  apparatus  will  now  be  apparent.  The 
cathode  hangers  bearing  the  articles  to  be  plated  are  hung  upon 
the.  conveyer  screws  15  at  suitable  intervals  while  the  screws  are 
rotating,  and  the  hanger  thus  progresses  on  one  of  the  conveyer 
screws  toward  the  transfer  rod  17,  passes  freely  through  the  open- 
ing at  tffe  bottom  of  the  intermediate  supporting  bearings  18, 
and  when  it  arrives  at  the  termination  of  the  coil  on  the  con- 
veyer screw,  it  is  engaged  by  one  of  the  transfer  fingers  41  of 
the  rotary  transfer  disk  35.  The  hanger  is  thereby  carried  from 
the  end  of  one  conveyer  screw  onto  the  transfer  rod  17  and 
finally  delivered  to  the  end  of  the  other  conveyer  screw  at  a  point 
where  it  will  be  engaged  by  the  coil  of  the  conveyer  screw  and 
started  on  its  return  through  the  bath.  The  negative  terminal 
of  the  current  is  connected  with  the  conveyer  screws  15,  so  that 
the  articles  carried  by  the  cathode  hangers  19  become  the  cathode 
in  the  bath  and  are  plated.  The  articles  to  be  plated  may  be  of 
such  weight  as  to  tend  to  distort  the  conveyer  screws,  but  by  the 


ELECTRO  GALVANIZING    PLANT    AND    EQUIPMENT          161 

provision  of  the  intermediate  supporting  bearings  such  tendency 
is  rendered  ineffective. 

In  the  apparatus  shown  and  described  the  articles  to  be  plated 
are  introduced  and  removed  from  the  same  end  of  the  vat  and 
in  order  to  maintain  the  cathode  surface  area  substantially  uni- 
form in  the  electroplating  operation,  it  is  advisable  to  avoid 
variations  in  the  number  of  the  articles  being  plated.  By  the 
arrangement  shown  the  maintenance  of  uniformity  in  this  respect 
is  facilitated  as  the  operator  standing  at  one  end  of  the  vat  in- 
troduces a  new  article  for  each  plated  article  withdrawn.  The 
rheostat  can,  therefore,  be  adjusted  in  starting  up  operations  to 
suit  the  particular  requirements,  but  after  the  number  of  articles 
in  the  vat  has  reached  full  capacity  no  further  regulation  of  the 
rheostat  is  necessary.  The  plating  thus  conducted  is  of  highly 
uniform  character  and  is  independent  of  the  judgment  of  the 
operator,  as  the  conditions  determining  the  character  of  the  plat- 
ing are  mechanically  controlled. 

The  Fleischer  Cable  or  Chain  Conveyer  Machine 

Figs.  62  to  65  show  a  cable  or  chain  conveyer  traveling  over 
numerous  rollers  and  so  placed  that  goods  suspended  on  knobs 
fastened  to  the  cable  will  travel  in  a  continuous  motion  from  one 
tank  into  the  other.  First,  cleaning;  second,  rinsing;  third,  plat- 
ing, and,  fourth,  drying.  This  apparatus  is  patented  by  Herman 
&  Charles  Fleischer  and  assigned  to  the  Stanley  Works  of  New 
Britain,  Conn. 

1  is  a  water-tight  tank  of  usual  form,  open  at  the  top.  The 
tank  1  receives  and  holds  the  plating  solution.  2,  2  are  anodes. 
3,  3  are  articles  to  be  plated,  which  will  hereinafter  be  termed  the 
"cathodes."  In  the  preferred  form  of  our  invention  both  the  anodes 
and  cathodes  are  mechanically  conveyed  into,  through  and  out  of 
said  plating  solution;  but  it  is  not  absolutely  essential  to  certain 
fundamental  features  of  the  invention  that  the  cathodes  themselves 
be  moved  through  said  solution. 

4.  4  are  bars,  which  we  term  "anode-carriers,"  the  same  being 
formed  of  suitable  conducting  material.  Both  ends  of  each  of  the 
anode-carriers  4  are  connected  to  drive  chains  or  belts  5,  5,  ar- 
ranged to  traverse  on  opposite  sides  of  the  tank,  each  chain  5 
traver&ing  over  a  series  of  independent  guide-sprockets  arranged 
on  opposite  sides  of  the  machine. 


162 


GALVANIZING  AND  TINNING 


6,  6  are  cathode-carriers,  from  which  are  suspended  the  cathodes 
3,  3.  Both  ends  of  each  cathode-carrier  are  attached  to  chains  7,  7, 
which  are  arranged  to  traverse  the  opposite  sides  of  the  tank  and 
are  guided  by  suitable  independent  sprockets,  also  located  on  oppo- 
site sides  of  the  machine. 


FIG.  62.    SIDE  ELEVATION  OF  FLEISCHER  MACHINE 


FIG.  63.  VIEW  OF 
FLEISCHER'S  MA- 
CHINE SHOWING 
C  A  E  R  I  E  R  AND 
CONVEYER 
CHAIN 


FIG.  64.  CROSS  SEC- 
TION OF  TANK  OF 
FLEISCHER  CHAIN 
CONVEYER  MACHINE 


FIG.  65.  ENLARGED  DETAIL 
VIEW  OF  TANK  SHOWING 
ANODES  IN  POSITION 


The  chains  5  and  7  are  driven  at  a  corresponding  rate  of  speed. 
Any  suitable  driving  means  may  be  provided.  For  example,  the 
guide-sprockets  8,  8  may  be  mounted  upon  a  shaft  8a,  so  that  when 
rotary  motion  is  imparted  to  one  of  said  sprockets  it  will  be  trans- 
mitted through  one  shaft  to  the  other  sprocket.  One  of  the 
sprockets  9,  traversed  by  chain  7,  may  act  as  the  drive-sprocket  for 
one  of  the  chains  7.  The  corresponding  guide-sprocket  on  the  other 
side  of  the  machine  (not  shown)  may  be  mounted  on  a  shaft  with 
the  guide-sprocket  9,  so  that  when  one  turns  the  other  will  turn. 
The  driving-sprockets  8,  9  may  be  connected  by  means  of  a  chain 
8b,  so  that  power  applied  to  either  of  the  sprockets  8  or  9  will 
be  transmitted  to  the  other.  In  the  preferred  construction  the 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT       ic>3 

sprockets  8,  9  are  rotated  intermittently  by  means  of  a  ratchet  10, 
pawl  11  and  rocking  arm  12. 

The  anode-carriers  4  are  spaced  apart  at  equal  intervals,  and 
the  cathode-carriers  are  spaced  apart  at  like  intervals.  When  the 
anodes  and  the  cathodes  are  being  conveyed  through  the  solution 
in  the  tank  1  it  is  preferred  that  said  anodes  and  cathodes  be 
spaced  apart  alternately  and  at  equal  intervals. 

13,  13  are  tracks  along  the  upper  opposite  edges  of  the  tank  1 
and  arranged  to  support  the  anode-carriers  4  while  the  anodes  are 
immersed  in  the  solution  in  tank  1.  14,  14  are  tracks  also  ar- 
ranged along  the  edges  of  the  tank  1,  their  function  being  to  sup- 
port the  cathode-carriers  6  when  the  cathodes  are  immersed  in  the 
solution.  To  prevent  interference,  the  tracks  14,  14  are  prefer- 
ably spaced  apart  a  less  width  and  are  at  a  lower  elevation  than 
the  tracks  13.  The  length  of  the  cathode-carriers  6  is  corre- 
spondingly less  than  the  length  of  the  anode-carriers  4.  One  or 
both  of  the  tracks  13  constitutes  electrical  contact  for  the  carrier  4. 
The  same  is  true  of  one  or  both  of  the  tracks  14,  the  same  being 
an  electrical  contact  for  the  cathode-carrier  6.  The  signs  plus  (-(-) 
and  minus  ( — )  represent  the  respective  electrical  connections. 
The  track  13,  being  the  anode  connection,  is  positive,  while  the 
track  14,  being  the  cathode  connection,  is  negative. 

The  chains  5  and  7  are  preferably  insulated  from  the  carriers 
4  and  6. 

15  is  a  bushing  of  insulating  material  provided  at  each  end 
of  the  carriers.  Pins  5%  carried  by  the  chain  5,  project  into  these 
insulating-bushings  15. 

The  guide-sprockets  over  which  the  anode-chains  5  run  are  so 
arranged  that  the  anodes  will  be  lowered  into  the  plating  solution 
at  one  end  of  the  tank,  whereupon  the  anode-carrier  will  make  elec- 
trical connection  with  the  track  13.  The  anodes  are  then  con- 
veyed through  the  solution  and  removed  from  the  other  end  of 
the  tank.  The  guide-sprockets  over  which  the  cathode-chains  7 
run  are  so  arranged  that  the  cathodes  will  be  lowered  into  the 
solution  alternately  with  the  anodes,  whereupon  the  cathode-carriers 
will  make  an  electrical  connection  with  the  track  14.  The  cathodes 
are  then  conveyed  through  the  plating  solution  and  removed  from 
the  other  end  of  the  tank.  While  in  the  solution  the  cathodes  and 
anodes  are  preferably  spaced  apart  at  equal  intervals.  While  in 
the  plating  solution  the  surfaces  of  the  anodes  will  become  fouled 


164  GALVANIZING  AND  TINNING 

by  a  scum-like  deposit,  which  if  allowed  to  accumulate  will  impair 
the  free  plating  action  and  dissolution  of  the  metal.  By  making 
the  anodes  automatically  removable  they  may  be  readily  cleaned — 
for  example,  by  causing  them  to  be  immersed  in  an  anode-cleansing 
bath,  which  may  be  provided  in  tank  15.  The  guide-sprockets 
16,  16,  17  are  so  arranged  that  each  anode  will  be  lifted  up  over 
the  edges  of  the  tank  15  and  immersed  for  a  short  time  in  the 
cleansing  solution  therein.  There  are  many  advantages  in  keep- 
ing the  anodes  clean,  among  which  are  rapidity  of  dissolution  of 
the  metal,  relatively  rapid  speed  and  uniformity  of  deposit,  saving 
in  electric  current  and  chemicals.  The  balance  of  the  guide- 
sprockets  for  the  anode-chain  not  already  numbered  are  indicated 
at  18,  18.  Obviously  the  particular  arrangement  of  the  guide- 
sprockets  and  the  method  of  supporting  them  is  entirely  immaterial. 

The  movement  of  the  chains  5,  7  is  so  comparatively  slow  that 
an  operator  standing  at  either  end  of  the  tank  may  remove  the 
plated  articles  from  the  cathode-carriers  6  and  substitute  unplated 
articles  which  in  due  course  will  be  conveyed  through  the  plating 
solution,  as  previously  described. 

By  causing  the  articles  to  be  passed  through  the  solution  alter- 
nately with  the  anodes,  each  line  of  articles  suspended  from  a 
cathode-carrier  is  moving  into  a  sphere  of  solution  which  has  been 
enriched  by  the  dissolution  of  the  anode  immediately  in  front  of 
it,  the  said  anode  practically  recharging  the  solution  which  has 
been  partially  impoverished  by  the  cathode  immediately  preceding 
said  anode. 

While  to  those  features  of  the  invention  already  described  it  is 
not  essential  that  the  apparatus  shall  have  the  capacity  of  pre- 
paring the  articles  to  receive  the  plating  deposit,  a  further  de- 
velopment of  the  invention  contemplates  the  continuation  of  the 
cathode-chains  7,  7  so  that  they  will  cause  the  cathode-carriers  <>,  i> 
and  articles  suspended  therefrom  to  traverse  a  washing-tank  19,  in 
which  tank  various  baths  may  be  provided  in  separate  compart- 
ments, into  which  the  articles  to  be  plated  may  be  successively 
immersed  in  order  to  prepare  the  surfaces  thereof  to  receive  the 
plating  solution.  We  have  found  that  great  economies  are  at- 
tained by  this  arrangement.  Not  only  is  the  danger  of  possible 
contamination  of  the  surface  of  the  article  rendered  practically 
impossible,  because  the  articles  are  not  manually  handled  after 
being  cleaned  and  until  they  are  plated,  but  a  decided  saving  in 


ELECTRO  OALVAXIZING    PLANT   AND   EQUIPMENT         165 

chemicals  results.  The  chains  7  traverse  in  the  direction  of  the 
arrows,  so  that  an  operator  standing  at  the  left-hand  end  of  the 
tank  may  attach  to  the  carriers  mounted  on  the  chain  7  the  articles 
to  he  plated.  These  articles  are  conveyed  into  the  several  prepara- 
tory baths  successively,  and  the  movement  is  so  comparatively 
slow  that  ample  opportunity  is  given  for  the  chemicals  to  drip  from 
the  articles  into  the  baths  from  which  they  are  removed  before  being 
immersed  in  another  bath  which  may  be,  for  example,  of  a  different 
chemical  nature.  This  drip  occurs  directly  over  the  bath  from 
which  the  article  is  removed,  and  hence  the  particular  chemicals 
therein  are  saved. 

The  danger  of  injury  to  operatives  by  contact  with  the  chemicals, 
incidental  to  the  cleansing  of  the  articles,  is  entirely  eliminated. 

20  is  a  final  washing-tank  at  the  opposite  end  of  the  plating- 
tank  into  which  the  plated  articles  are  immersed  after  being  re- 
moved from  the  plating  solution. 

21,  21  represent  the  sprockets  for  the  chain  7  whereby  said  chain 
is  moved  in  such  a  course  that  the  cathode-carriers  supported  by 
said  chain  will  be  conveyed  in  such  a  direction  as  to  move  the 
articles  to  be  plated  over  each  of  the  partitions  in  the  tanks  19 
and  20,  so  that  the  said  articles  will  be  washed  or  immersed  in 
the  aforesaid  baths.  The  particular-  arrangement  of  these  sprockets 
21  is,  of  course,  immaterial  so  long  as  they  permit  of  the  use  of 
endless  bands  or  belts  7. 

These  foregoing  illustrations  show  the  different  ways  and  means 
which  can  be  adopted  to  improve  the  plating  of  larger  articles 
in  open-tank  work. 

The  Daniels  Plating  Barrel 

Figs.  66  to  69  show  a  plating  barrel  suspended  on  a  shaft 
with  a  special  connection  carrier.  The  barrel  is  of  the  perforated 
type  and  is  immersed  entirely  in  the  solution.  Curved  anodes  have 
to  be  used  to  secure  a  better  current  conductively  all  around  the 
barrel.  The  center  shaft  within  the  barrel  is  provided  with  chains 
to  connect  the  work  with  the  negative  current  of  the  dynamo.  By 
loading  and  unloading  the  goods  to  be  plated  in  this  barrel,  the 
barrel  must  be  lifted  from  the  solution  and  connections  by  means 
of  a  lifting  device.  This  machine  is  patented  by  the  Hanson  &  Van 
Winkle  Company  of  Newark,  N".  J. 

Fig.  68  is  a  longitudinal  vertical  section  of  one  form  of  electro- 


166  GALVAXTZIXG  AND  TINNING 

plating  apparatus,  and  one  form  of  revoluble  container,  drum  or 
cylinder,  mounted  upon  a  shaft  or  spindle,  said  view  illustrating 
in  elevation,  a  number  of  flexible  contacts  or  cathode-elements  em- 
bodying the  principles  of  this  invention. 

1  is  the  tank,  comprising  base  2,  sides  3  and  ends  4.  5  is  one 
of  the  two  usual  and  similar  anode  bars  from  which  the  anodes  5' 
are  suspended  on  either  side  of  the  drum  or  container  8.  These 
bars  it  are  secured  to  the  tank  bv  fasteners,  as  (>,  and  are  con- 


fe 


FIG.  60.    HAND  WHEEL  LIFTING  DEVICE  FOR  DANIELS  BARKEL 


nected  by  means  of  the  connector  7  with  the  wire  7',  which  connects 
with  the  positive  terminal  of  an  electric  generator. 

The  mass  of  articles  8'  is  placed  within  drum  8,  which  is  rigidly 
mounted  on  shaft  9,  rota table  in  bearings  11  of  removable  suspen- 
sion frame  10  having  members  12  removably  engaging  with  and 
supported  by  rods  13  secured  to  and  extending  across  tank  1,  and 
through  connector  13'  and  wire  13"  connected  with  the  negative 
terminal  of  an  electric  generator.  Shaft  9  is  driven  from  a  shaft 
member  14  by  any  convenient  power,  a  separate  connection  between 
said  shaft  and  member  being  made,  in  this  instance. 


KLKCTRO  GALVANIZING   PLANT    AND    EQUIPMENT          1C7 

The  novel  cathode  members,  or  elements,  are  loosely  and  movably 
combined  with  and  supported  by  shaft  9,  from  which  they  depend. 
They  comprise,  in  this  instance,  a  weight  or  sinker-portion  19,  a 


FIG.   07.    LEVEK   LIFTING  JJEVICL   :-„>   DANIELS   BARREL 


•I 


3S3  $-«wa 

i 


FIG.  6S.    VERTICAL  SECTION  OF  DANIELS  PLATING  BARREL 

coupling  portion  comprising  ring,  or  eye,  16  loosely  encircling  shaft 
9,  and  an  intermediate  flexible  portion,  in  this  instance  a  section 
of  chain  18,  the  upper  link  of  which  is  connected  with  an  eye  or 


168 


GALVANIZING  AND  TINNING 


hook-shaped  part  17  of  a  stem  or  rod  15,  thereby  loosely  con- 
necting 15  with  19  as  shown. 

During  the  rotation  of  the  drum  the  articles  to  he  electroplated 
are  tumbled  about  within  said  drum,  constantly  exposing  new  sur- 
faces, and  making  efficient  contact  with  the  weight  or  sinker-portion 
19  of  the  cathode-member. 


FIG.  69.    TRANSVERSE  SECTION  OF  DANIELS  PLATING  BARREL 

The  Potthoff  Automatic  Galvanizing  Barrel 

Figs.  70  and  71  show  an  apparatus  patented  by  Louis  Potthoff, 
«f  the  United  States  Electro  Galvanizing  Co.  of  Brooklyn,  N.  Y. 
Fig.  70  shows  that  the  plating  barrel  is  resting  in  bearings 
and  center  shaft  on  top  of  a  plating  tank,  immersing  the  plat- 
ing barrel  only  about  one-third  into  the  solution.  It  also  is  pro- 
vided with  inside  anodes  supported  through  a  center  shaft  and 
special  anodes  supports  to  prevent  the  articles  from  coming  in  con- 
tact with  the  anodes.  After  the  articles  have  been  plated  the  spring 
door  is  set  and  the  goods  will  be  discharged  little  by  little  into 
Ihe  washing  drum  and  carried  from  here  in  a  screw  conveyer  into 
the  drying  drum  and  then  finally  into  a  tray. 

The  tumbling  barrel  1  is  mounted  on  a  shaft  supported  on  the 
solution  tank  2  by  bearings  3.  Tumbling  barrel  1  is  rotated  by 
means  of  sprocket  4  and  chain  5.  On  the  opposite  side  of  barrel  1 
is  a  sprocket  6  with  driving  chain  7,  which  actuates  the  sprocket  8 
on  one  end  of  shaft  9,  shaft  9  being  journaled  in  bearing  10,  sup- 
ported on  tank  2.  Shaft  9  is  provided  with  bevel  bear  11,  meshing 


ELECTRO  GALVANIZING    PLANT    AND    EQUIPMENT          Ifi!) 

with  uvar  \~  positioned  at  one  end  of  shaft  13.  Shaft  13  is  pro- 
vided with  a  hearing  11  in  proximity  to  gear  12.  Mounted  upon 
shaft  13  are  the  washing  drum  15,  draining  drum  16,  and  drying 


FIG.   70.    POTTHOFF  AUTOMATIC  GALVANIZING  BARBEL 

drum  IT.  Shaft  13  is  preferably  slightly  inclined  to  assist  the 
progressive  movement  of  articles  treated  in  washing  drum  15,  drain- 
ing drum  10,  and  drying  drum  IT. 

When  the  tumbling  barrel  1  is  rotated  in  the  direction  of  the 
arrow  18  the  contained  material  is  subjected  to  the  combined 
tumbling  and  plating  treatment,  and  at  the  same  time  the  devices 
for  subsequent  mechanical  handling  of  the  material  are  operated 
to  progress  the  material  through  the  various  operations  and  finally 
sorted  and  collected  in  a  suitable  receptacle  for  shipment  or  storage. 

Tumbling  barrel  1  comprises  a  barrel  having  its  inner  periphery 
covered  witli  porous  material,  preferably  cocoa-matting  21,  upon 
which  strips  20  are  placed,  in  which  strips  20  there  are  provided 
holes  of  such  size  as  to  prevent  the  articles  treated  in  barrel  1  from 
projecting  therethrough.  For  the  cocoa-matting  covering  are 


170 


GALVANIZING  AND  TINNING 


claimed  many  advantages  over  material  heretofore  employed  for 
this  purpose,  for  by  means  of  cocoa-matting  the  articles  are  given 
a  high  polish,  and  no  obstruction  is  offered  by  the  cocoa-matting 
to  the  passage  of  the  electric  current.  Strips  20  may  be  made  of 
wood  or  other  insulating  material.  The  barrel  1  is  supported  on 
tank  2  by  means  of  spiders  22  joined  to  shafts  of  sprockets  4  and 
6,  respectively. 


FIG.  71.    SECTION  OF  POTTHOFF  AUTOMATIC  GALVANIZING  BARREL 

Within  barrel  1  a  pocket  23  is  formed  by  extending  across  the 
barrel  an  inclined  plate  making  an  angle  with  the  curved  side  of 
barrel  1,  and  a  pivoted,  automatically  actuated  door  24  closes  the 
opening  at  the  end  of  pocket  23.  As  shown,  the  pocket  23  extends 
transversely  across  barrel  1,  opening  within  said  barrel  so  that 
when  said  barrel  is  rotated  in  the  direction  of  arrow  25  articles 
will  be  ^caught  by  pocket  23  and  will  be  in  a  position  to  be  dis- 
charged ttpon  the  automatic  opening  of  door  24.  Door  24  is  pro- 
vided with  springs  26  and  latching  devices  whereby  to  automatically 
open  the  door  upward  when  the  latching  devices  are  tripped. 

On  the  ends  of  barrel  1  are  pivoted  latches  2?  controlled  by 
springs  28.  Latches  27  co-operate  with  pins  29  on  the  door  24, 
so  that  normally  latches  27  hold  the  door  24  in  closed  position 
against  the  tension  of  springs  26. 

Supported  by  standards  30  on  tank  2  are  pivoted  tripping  fingers 
31,  one  end  of  each  finger  31  co-operating  with  each  of  the  latches 
27,  the  other  end  of  each  finger  31  being  weighted  and  further 
provided  with  a  lug  32  contacting  with  standard  30  to  maintain 
normally  each  finger  31  in  a  horizontal  position  and  preventing 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  171 

further  rotation  in  the  counter-clockwise  direction.  When  barrel 
1  is  rotated  in  the  direction  of  arrow  18  the  latches  27  will  depress 
the  fingers  31  without  being  tripped,  but  upon  reversal  of  rotation 
in  the  direction  of  arrow  25  fingers  31  will  trip  latches  27,  allow- 
ing the  door  24  to  open  automatically  and  permit  material  caught 
in  pockets  23  to  be  discharged  from  barrel  1  outside  the  plating 
tank. 

Mounted  on  tank  2  on  the  opposite  side  are  stationary  cams  33, 
which  are  engaged  by  pins  29  to  close  and  latch  the  door  24. 
This  occurs  upon  continued  reverse  rotation  of  the  plating  barrel, 
and  the  door  will  again  automatically  open  to  discharge  a  further 
quantity  of  material  caught  by  pocket  23  when  the  latch  27  is 
again  tripped. 

Chute  34  is  pivoted  on  funnel  member  35,  which  is  mounted 
on  washing  tank  36  by  means  of  arms  37. 

Washing  drum  15  is  composed  of  perforated  material  mounted 
on  shaft  13  by  means  of  a  spider  38.  At  one  end  there  is  an 
opening  registering  with  funnel  member  35,  and  at  the  opposite 
end  is  a  pocket  39  positioned  so  that  articles  contained  in  the 
drum  when  rotated  in  the  direction  of  the  arrow  19  will  be  caught 
in  pocket  39  and  discharged  into  the  draining  drum  J.6.  Draining 
drum  16  is  preferably  connected  with  washing  drum  15,  and,  as 
shown,  may  be  similarly  constructed  of  perforated  material. 

Connected  with  draining  drum  16  and  having  an  opening  re- 
ceiving the  discharge  from  pocket  39  is  the  drying  drum  17,  which 
may  be  supported  by  a  spider  41.  The  drying  drum  17  may  be 
formed  of  perforated  material,  and  with  an  outer  covering  of 
asbestos  or  similar  material.  Drying  drum  17  is  preferably  pro- 
vided also  with  a  stationary  housing  42. 

43  is  a  heater  disposed  below  the  drum  17,  shown  as  a  plurality 
of  gas  jets,  but  obviously  any  other  type  of  heating  means  may 
be  employed.  Drying  drum  17  is  further  provided  with  a  com- 
bined discharging  pocket  and  chute  44,  which  pocket  44  is  so 
positioned  that  articles  are  caught  therein  at  the  bottom,  and  dis- 
charged at  the  top,  when  the  drum  is  rotated  in  the  direction  of 
the  arrow  19. 

The  washing  drum  is  of  such  diameter  or  so  positioned  as  to 
be  partially  immersed  in  the  washing  liquid  in  tank  36,  which 
washing  liquid  may  be  continuously  replenished  by  means  of  suit- 
able supply  and  discharge  pipes.  The  draining  drum  16  is  of 


172 


GALVANIZING  AND  TINNING 


smaller  diameter  than  the  washing  drum  15,  and,  preferably,  one 
end  of  draining  drum  16  bears  upon  the  upper  side  of  tank  36, 
the  bearing  friction  being  relieved  by  anti-friction  roller  devices  45 
co-operating  with  a  bearing  ring  46  on  draining  drum  16. 

The  Schulte  Mechanical  Galvanizing  Barrel 

Illustration  72  shows  a  plating  machine  resting  and  travel- 
ing on  two  rings,  one  acting  as  a  gear  and  the  other  as  a  current 
connector.  It  is  substantially  constructed  of  2-in.  cypress.  The 
standard  size  barrel  is  36  in.  in  diameter  and  12  in.  wide,  resting 
in  a  tank  53  in.  long,  21  in.  wide  and  33  in.  deep  (inside  measure- 
ments). 


FIG.  72.    SCHULTE  MECHANICAL  GALVANIZING  BARREL 

The  apparatus  is  also  constructed  so  as  to  allow  a  largo  amount 
of  anode  surface  within  the  drum  without  interfering  with  the  arti- 
cles to  be  plated;  doing  away  entirely  with  the  necessity  of  perfora- 
tions, making  it  possible  to  plate  successfully  the  smallest  articles 
such  as  needles,  pins,  rivets,  screws,  etc.  The  drum  in  traveling 
clockwise  subjects  the  articles  thoroughly  to  the  action  of  the  elec- 
tric current,  thus  plating  evenly. 

The  most  important  features  of  this  new  apparatus  are  the 
methods  of  loading  and  unloading  of  its  contours.  These  are 
shown  in  Figs.  73  and  74. 

The  lid  is  removed  from  the  drum  and  the  loading  of  the  articles 
is  done  as  shown  in  the  illustration,  without  removing  the  drum 
from  the  solution  and  disconnecting  it  from  the  plating  current. 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  173 

The  unloading  of  the  articles  plated  from  the  drum  is  done  in 
the  simplest  manner.  The  perforated  carrier  is  inserted  in  the  place 
of  the  lid  and  in  one  revolution  of  the  drum  is  filled.  This  opera- 


FIG.  73.   LOADING  SCHULTE  BARBEL 


FIG.  74.    UNLOADING  GALVANIZED  ARTICLES  FROM  SCHULTE  BARREL 


174 


GALVANIZING  AND  TINNING 


tion  is  repeated  until  the  entire  finished  plated  articles  are  removed 
leaving  the  solution  intact  in  the  drum  and  ready  for  repeated  use. 

The  Ele-Kem   Galvanizing   Barrel 

A  saw-toothed  barrel  lining  is  the  chief  feature  of  this  construc- 
tion. The  object  of  this  is  twofold.  First,  that  the  articles  to  be 
plated  may  be  thoroughly  subjected  to  the  action  of  the  electric 
current.  As  the  barrel  rotates  from  left  to  right,  it  will  be  noted 


FIG.  *75.     SIDE  VIEW  OF  ELE-KEM  BARREL  WHEN  USED  AS  A  DRYER 


that  the  load  is  carried  successively  on  these  saw-teeth  and  when 
reaching  the  half  turn,  the  load  is  shoveled  over  so  that  every  part 
of  the  mass  to  be  plated  is  presented  to  anodic  action. 

The  saw-tooth  construction  has,  however,  a  second  mission  equally 
important  to  the  first,  in  that  it  does  away  with  the  necessity  of 
removing  the  barrel  for  the  discharge  of  its  contents.  It  will  be 
seen  that  as  the  barrel  rotates  from  left  to  right,  when  the  action 
is  reversed,  a  part  of  the  plated  mass  is  carried  up  on  the  angle 
of  the  saw-teeth  and  is  discharged  on  a  receiving  trough  or  chute. 
The  continuance  of  the  rotation  insures  the  depositing  of  the 
entire  plated  load  down  to  the  last  rivet,  screw  or  buckle.  From 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT 


175 


the  trough,  which  receives  the  articles  so  deposited,  the  load  is 
raked  by  the  operator  or  the  slope  of  the  trough  can  be  so  ad- 
justed as  to  carry  the  load  out  by  gravity. 

The  barrel  construction  can  be  used  by  modifications  of  its  form 
for  the  purposes  of  plating,  burnishing  or  drying.  The  barrel  is 
substantially  constructed  of  2-in.  cypress  or  oak,  as  desired.  The 
standard  plating  barrel  is  3  ft.  in  diameter  and  3  ft.  in  length. 
It  has  a  14-inch  opening  in  the  fron".;  through  which  the  goods 


FIG.  76.   DETAILS  OF  ELE-KEM  BARREL 

are  charged  and  discharged.  In  the  standard  barrel  there  are  eight 
saw-tooth  steps.  These  thoroughly  mix  the  articles  by  the  shovel- 
ing process  referred  to  and  effectively  prevent  their  sliding  en  masse. 
The  barrel  rests  in  a  tank  2  ft.  deep,  3  ft.  6  in.  in  length  and 
3  ft.  6  in.  wide  and  is  driven  by  a  worm  and  gear  with  a  reverse 
pulley.  When  the  apparatus  is  running  clockwise,  the  articles  are 
plated  and,  by  reversing  the  movement  by  means  of  the  shafting 
belt,  the  goods  are  unloaded,  as  previously  described,  011  a  per- 
forated chute.  The  goods  can  be  raked  or  shoveled  into  a  con- 
tainer, pail  or  tray,  from  which  they  can  be  transferred  to  the 
hot  water  or  into  a  drying  machine. 


176 


GALVANIZING  AND  TINNING 


In  addition  to  the  outside  anodes,  there  is  an  inside,  adjustable 
flat  anode  hooked  to  the  hollow,  central  shaft,  both  connected  and 
renewed.  The  means  of  connection  are  novel.  The  shaft  is  hollow 


FIG.  7fc    SECTION  SHOWING  SAWTOOTHED  LINING  OF  ELE-KEM  BARREL 

and  through  it  runs  a  copper  rod  insulated  by  a  rubber  hose  and 
an  extension  from  this  rod  leads  into  the  solution  on  the  inside  of 
the  barrel  and  makes  connection  with  the  goods  to  be  plated. 

In  Fig.  75  will  be  noted  the  barrel  adapted  for  drying  purposes. 
It  is  made  out  of  perforated  galvanized  sheet  metal  and  installed 
in  an  iron  tank  holding  hot  water.  The  barrel  is  driven  by  a 
sprocket  wheel  and  a  belt  on  a  small  shaft.  The  goods  to  be 
dried  are  placed  at  the  rear  opening  of  the  drum  and  are  ele- 
vated in  the  course  of  rotation  and  discharged  through  a  per- 
forated cylinder  extending  in  front  of  the  drum,  and  thence  into 
a  suitable  container.  In  handling  castings  or  any  other  material, 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT 


177 


the  hot  water  is  sufficient  to  bring  about  a  satisfactory  drying.  For 
small,  light  articles  or  stampings,  a  steam  coil  is  placed  beneath 
the  extended  cylinder.  In  special  cases  a  compressed  air  supply  is 
delivered  to  the  inside  of  the  drum  and  forced  through  the  goods, 


JO- 

i't 

1 
I 

k  S&               s? 

t" 

.2 
X? 

SHsiffi 

; 
"  «»*»  °°°  ' 

ol'al     If?    - 

1  iHSil!!  I 

2(J 

. 

|ggSSS3  = 

1    ^^          p 

FIG.   78.    DETAILS  OF  LINING  AND  SHAFT  CONNECTIONS 

thus  insuring  absolute  drying  and  doing  away  with  the  necessity 
of  using  sawdust,  etc. 

This  machine  is  patented  by  Louis  Schulte  and  sold  by  the  Ele- 
Kem  Company  of  Chicago. 

A  Cleaning.  Rinsing  and  Plating  Barrel  Unit 

Figs.  79  to  8-i  give  a  view  and  details  of  a  plating  barrel  of 
a  smaller  type  so  constructed  that  it  easily  can  be  removed  from 
one  tank  into  another  and  thereby  allow  the  cleaning,  rinsing  and 
plating  to  be  done  without  removing  the  articles  from  the  barrel 
from  the  start  until  the  complete  process  is  accomplished.  The 


178  GALVANIZING  AND  TINNING  ' 

plating  container  or  barrel  travels  on  a  ring  fastened  through 
spokes  to  the  walls  of  the  barrel  and  the  ring  travels  on  a  small 
sprocket  wheel,  set  in  motion  by  a  belt  or  little  motor.  This 
machine  is  patented  by  Louis  Schulte  of  Chicago. 

By  the  system  of  cleaning,  rinsing  and  plating  without  handling 
the  articles,  it  not  only  reduces  time  lost  in  preparing  articles  to 
be  plated,  but  increases  the  output  with  less  labor. 

The  mechanical  plating  barrel,  as  shown  by  the  accompanying 
cut,  has  three  wooden  tanks  with  a  rotating  shaft  on  each  one; 
on  the  end  of  this  shaft  is  mounted  a  sprocket  wheel  which  en- 
gages with  the  carrier  ring  supporting  the  basket  or  barrel. 


%FIG.  79.    FBONT  VIEW  OF  COMPLETE  PLATING  UNIT 

The  carrier  ring,  being  perforated  to  engage  the  teeth  on  the 
small  driving  wheel,  insures  a  positive  drive. 

The  three  rotating  shafts  are  connected  by  means  of  sprocket 
wheels  and  chains,  which  are  driven  by  motor  or  belt  from  first 
tank. 

Pig.  82  is  a  top  plan  view  of  an  electroplating  device  embodying 
a  modified  form  of  the  machine.  Fig.  83  is  a  vertical  longitudinal 
section  of  the  device  shown  in  Fig.  82.  Fig.  84  is  a  vertical  trans- 
verse section  taken  on  line  y — y  of  Fig.  82. 

The  preferred  form  of  construction,  as  illustrated  in  the  draw- 
ings, comprises  a  tank  1  formed  of  non-conductive  material,  said 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT          179 

tank  being  open  at  its  upper  side.  Arranged  at  the  upper  edge 
of  the  tank  1  is  a  shaft  2  which  is  mounted  in  suitable  bearings 
3  and  4.  Provided  at  the  outer  end  of  the  shaft  2  is  a  pulley 
5  adapted  for  engagement  by  a  belt  in  rotating  the  shaft  2.  Pro- 
vided at  the  inner  end  of  the  shaft  2  is  a  gear  6.  The  gear  6 
meshes  with  an  annular  internal  gear  7,  which  depends  therefrom 
into  the  tank  1  as  clearly  shown,  the  gear  7  resting  loosely  upon 
the  gear  6,  the  same  being  held  in  mesh  with  said  gear  6  through 


FIG.  80 — VERTICAL  TRANSVERSE 
SECTION 


FIG.    81 — SECTION   SHOWING 
CONTAINER 


gravity.  The  opposite  sides  of  the  gear  7  are  provided  with  in- 
wardly extending  flanges  8,  which  serve  to  hold  said  gear  in  mesh 
with  the  gear  7,  a  channel  being  thus  formed.  Surrounding  the 
outer  side  of  gear  7  and  the  corresponding  sides  of  flanges  8  is  a 
covering  9  of  insulating  material,  preferably  rubber.  With  the  ar- 
rangement disclosed  it  will  be  seen  that  upon  rotation  of  the 
shaft  2  gear  7  will  be  propelled  thereby,  the  latter  being  caused 
to  rotate  in  the  tank  1,  as  will  be  readily  understood. 


180  GALVANIZING  AND  TINNING 

Arranged  centrally  in  the  gear  7  is  a  holder  or  container  for 
the  articles  which  it  is  desired  to  plate.  This  holder  comprises  a 
hollow  foraminated  body  10  of  non-conductive  material  such  as 
wood,  and  a  conductive  frame  formed  preferably  of  metal,  which 
consists  of  the  annular  angular  members  11,  which  are  arranged 
at  the  opposite  sides  of  the  body  1  and  connecting  bars  12  which 
extend  between  the  members  11  at  intervals.  The  members  11 
and  12  are  so  arranged  that  surfaces  thereof  will  be  exposed  to 
the  interior  of  the  holder  container  and  so  that  in  use  articles  ar- 
ranged in  the  body  10  will  contact  with  said  surfaces  and  thus  es- 
tablish an  electrical  connection  between  said  articles  and  the  frame 
of  said  body.  Said  body  frame  is  rigidly  secured  to  the  gear  7 
through  the  medium  of  radiating  bars  13  also  of  conductive  ma- 
terial, and  so  that  in  use  the  electrical  current  passing  through  the 
goods  contained  in  the  holder  will  pass  through  the  frame  mem- 
bers 11  and  12,  through  the  arms  13  and  thence  through  gear  7  and 
gear  6  meshing  therewith  to  the  shaft  2  to  complete  the  electrical 
circuit  as  hereinafter  described. 

A  section  14  of  the  peripheral  wall  of  the  body  10  is  slidably 
mounted  in  order  to  constitute  a  door  for  gaining  access  to  the  in- 
terior of  said  body,  the  lateral  edges  of  the  section  14  being  in  dove- 
tail connection  with  the  adjacent  edges  of  said  body,  the  frame 
member  11  at  one  side  being  cut  away  as  at  15  in  order  to  afford 
clearance  for  said  section  as  will  be  readily  understood.  The  door 
section  14  is  releasably  secured  in  closed  position  through  the  me- 
dium of  a  suitable  locking  device  16.  The  inwardly  extending 
flanges  of  the  frame  member  11,  at  the  opening  which  is  formed 
upon  removal  of  the  door  14  are  cut  away. 

Arranged  in  the  tank  1  adjacent  the  upper  edge  thereof  and  at 
either  side  of  the  holder  or  container  are  bars  17  from  which  de- 
pend anode- forming  electrodes  18.  Upon  bearing  3  and  corre- 
sponding extremities  of  the  bars  17  are  binding  posts  19  and  20 
respectively  for  connecting  the  same  with  a  source  of  electrical 
energy.  The  circuit  which  is  thus  formed  includes  the  frame 
members  11  and  12  of  the  holder  or  container  which  form  cathodes 
and  the  electrodes  18  which  constitute  anodes,  said  electrodes  be- 
ing electrically  connected  in  order  to  close  the  circuit  by  the  elec- 
trolyte which  is  introduced  into  the  tank  1  in  the  electroplating 
process  and  the  articles  arranged  in  holder  for  plating. 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  181 

Operation  of  the  Plating  Barrel 

First,  place  the  articles  to  be  plated  in  the  rotating  basket. 

Second,  suspend  basket  011  rotating  sprocket  on  cold  electric 
cleaning  tank  for  a  sufficient  length  of  time  to  clean  the  work.  This 
depends  upon  the  condition  of  the  same  and  may  require  from 
five  to  fifteen  mimitt-s. 

Third,  transpose  the  basket  from  cleaning  tank  to  the  rinsing 
tank,  letting  the  basket  rotate  in  the  rinsing  tank  for  a  period  of 
two  to  three  minutes. 

Fourth,  then  transpose  the  basket  from  the  rinsing  tank  to  the 
plating  tank — allowing  it  to  rotate  therein  long  enough  to  obtain 
a  plate  sufficient  for  the  requirements. 

A  plate  may  be  obtained  in  fifteen  to  twenty  minutes  that  will 
stand  bulling  without  cutting  through. 

After  removing  articles,  they  are  dried  in  the  usual  way. 

In  operating  the  device,  the  articles  which  it  is  desired  to  plate 
are  first  introduced  into  the  holder  or  container  body  10  through  the 
door  14.  If  it  is  desired  to  clean  the  articles  before  electroplating, 
a  cleansing  liquid  is  introduced  into  the  tank  1  and  the  container 
revolved  therein  through  operation  of  the  shaft  2.  After  cleansing 
and  rinsing  of  the  articles  the  container  is  placed  in  another  tank  1 
in  which  an  electrolyte  is  provided  or  if  desired  the  same  will  be 
permitted  to  remain  in  the  tank  1  from  which  the  cleansing  liquid 
has  been  removed  and  into  which  the  electrolyte  has  been  intro- 
duced. The  container  is  then  rotated  as  before  in  the  electrolyte. 
When  this  is  done  it  will  be  seen  that  the  articles  resting  in  con- 
tact with  the  frame  members  11  and  12  of  the  container  body  will 
become  the  cathode  in  the  electrical  circuit  to  which  the  current 
will  flow  through  the  electrolyte  from  the  anode-forming  elec- 
trodes 18,  thu,  effecting  the  plating  of  said  articles  as  will  be 
readily  understood.  After  the  articles  have  thus  been  plated  the 
container  may  be  removed  from  the  tank  1  by  disengaging  the 
gear  7  from  the  gear  6,  such  disengagement  being  readily  effected 
since  the  gear  T  simply  rests  upon  the  gear  6  as  above  described. 
After  the  coat  or  plating  has  dried  upon  the  articles,  the  container 
may  be  rotated  as  before  in  the  empty  tank  1  in  order  to  effect 
burnishing  or  polishing  thereof,  it  being  clear  upon  rotation  of 
such  container  the  articles  will  rub  against  each  other  and  thereby 
polish  the  same  as  desired. 

It  is  thus  seen  that  with  the  construction  set  forth,  the  entire 


182  GALVANIZING  AND  TINNING 

electroplating  process  may  be  carried  on  without  necessitating  the 
removal  of  the  articles  treated  from  the  container  in  which  the  same 
are  arranged  at  the  commencement  of  the  treatment,  the  articles 
being  removed  from  said  container  only  upon  completion  of  the  elec- 
troplating. This  is  rendered  possible  by  reason  of  the  detachable 
arrangement  of  the  container  in  the  tank,  said  container,  where  a 
plurality  of  tanks  are  used  in  the  process,  being  simply  removed 
from  one  tank  and  placed  in  another  as  will  be  readily  understood. 
Further  with  this  construction  the  loss  of  electrical  energy  is  ob- 
viated, since  with  this  construction  the  circuit  is  closed  upon  the  in- 
sertion of  the  container  in  the  tank  or  when  gear  7  contacts  with 
the  gear  6  and  broken  when  said  container  is  removed  from  the  tank 
or  when  the  gear  7  is  disengaged  from  the  gear  6,  the  circuit  being 
thus  closed  only  when  the  container  is  in  operative  position.  Also 
with  this  construction  the  necessity  of  a  hand  operable  switch  is 
dispensed  with  since  the  breaking  and  closing  of  the  circuit  is  auto- 
matically effected  upon  removal  or  insertion  of  the  container  in  the 
tank. 

Numerous  other  advantages  of  the  construction  which  it  is  not 
necessary  here  to  mention  will  be  apparent  to  those  skilled  in  the 
art. 

A  Modified  Form  of  the  Cleaning,  Rinsing  and  Plating 
Barrel  Unit 

Figs.  82  to  84  show  a  construction  which  is  a  slight  modification  of 
that  just  described.  In  this  construction  the  container  10  is  longer 
than  that  of  the  preferred  form  and  at  each  end  of  said  container  is 
provided*a  gear  7  and  the  parts  which  co-operate  therewith  to  which 
the  respective  ends  of  said  container  are  connected  in  the  same  man- 
ner as  the  gear  7  is  connected  with  the  container  body  10  in  the 
preferred  form.  The  gears  7  of  the  modified  form  mesh  with  gears 
21  which  are  provided  at  the  respective  ends  of  a  shaft  22  which  is 
mounted  in  suitable  bearings  23  provided  upon  cross  pieces  24  which 
rest  loosely  upon  the  upper  edges  of  opposing  walls  of  the  tank.  The 
arrangement  is  such  as  will  be  observed  that  upon  rotation  of  the 
shaft  22  the  container  10  depending  therefrom  will  be  rotated  in 
the  same  manner  as  the  container  10  of  the  preferred  form.  The 
removal  of  the  container  in  the  modified  form,  however,  is  effected 
by  engaging  the  opposite  ends  of  the  cross  pieces  24  which  are 
formed  into  grips  or  handles  as  shown  for  this  purpose.  Rotation 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT 


183 


of  the  shaft  22  is  secured  through  the  medium  of  a  gear  25  which 
is  fixed  to  said  shaft  midway  the  ends  thereof.  The  gear  25  meshes 
with  a  gear  26  provided  upon  a  shaft  27  which  is  mounted  at  the  free 
end  of  a  rocking  hearing  arm  28,  the  opposite  end  of  said  arm  28 
being  fulcrumed  to  a  shaft  29  which  is  mounted  in  hearings  29'  pro- 
vided at  the  upper  edge  of  the  tank  1  as  shown  in  Figs.  82  and  84. 
The  shaft  2T  is  operatively  connected  with  the  shaft  29  through  a 
belt  30  which  passes  around  pulleys  31  provided  upon  said  shafts 


FIG.  82 — PLAN  OF  MODI- 
FIED FORM  OF  THE 
BARREL  AND  TANK 


FIG.  84 — TRANSVERSE 
SECTION  OF  THE  BAR- 
REL AND  TANK 


FIG.  83 — VERTICAL  SECTION  OF  MODIFIED  FORM 
OF  THE  BARREL 

as  shown.  The  shaft  29  is  also  provided  with  a  pulley  32  for  con- 
nection thereof  by  means  of  a  belt  33  with  any  suitable  source  of 
power  .supply.  With  the  arrangement  disclosed  it  will  be  seen  that 
the  gear  2(5  rests  loosely  in  contact  with  the  gear  25,  said  gears  be- 
ing held  in  mesh  by  the  weight  of  the  gear  26  and  the  bearing  arm 
28,  and  so  that  when  it  is  desired  to  remove  the  container  10  said 
arm  28  may  be  rocked  upwardly  and  outwardly  to  disengage  the 
gear  26  and  permit  of  lifting  of  the  container  out  of  the  tank.  The 
operation  of  this  construction  is  precisely  the  same  as  that  above 
described,  anode-forming  electrodes  18  being  used,  which  are,  how- 
ever, arranged  along  the  lateral  wall  or  sides  of  the  container  10 
instead  of  at  the  ends  of  the  container  as  shown  in  Figs.  80  and  81. 


184 


GALVANIZING  AND  TINNING 


The  Meaker  Continuous  Type  Machine 

Figs.  85  and  86  show  a  machine  of  the  continuous  type  fixed 
with  horizontal  anodes  and  a  rocking  device  for  supplying  or  load- 
ing the  machine.  From  the  rocker  the  goods  are  conveyed  over  a 
perforated  tray,  connected  with  the  negative  current.  This  tray  is 
continuously  rocking  or  shifting  in  a  downward  horizontal  position 

FIG.  85.    TOP  PLAN  OF  MEAKER  CONTINUOUS  TYPE  MACHINE 


FIG.  86.    SIDE  ELEVATION  OF  MEAKER  CONTINUOUS  TYPE  MACHINE 

and  will  finally  deliver  the  plated  goods  onto  an  unloading  tray  into 
the  rinsing  tank.  This  machine  is  the  patent  of  G.  L.  Meaker  of 
Chicago. 

In  said  drawings:  A  indicates  a  tank  for  the  electrolyte.  Said 
tank  may  of  course  he  of  any  suitable  size,  form  or  material,  but  as 
shown,  is  an  elongated  rectangular  trough  constructed  of  wood  or 
any  material  not  adapted  to  injuriously  affect  or  be  affected  by  the 
electrolyte.  B  indicates  a  transverse  shaft  or  rod  extending  through 
the  sides  of  said  tank  somewhat  above  the  bottom  and  affording  con- 
nection for  one  of  the  conductors  from  the  generator  B'  or  other 
source  of  current.  Slidably  supported  near  its  lower  or  discharge 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  185 

'end  on  said  shaft  B  is  a  frame  C  comprising  parallel  side  rails  c  and 
an  upper  end  rail  c1.  Extending  transversely  beneath  and  connect- 
ing said  side  rails  c,  are  bars  c2,  which  are  rigidly  bolted  through 
the  side  rails  c,  as  shown  in  Figs.  85  and  86,  and  on  which,  adjacent 
each  of  said  side  members  c,  arid  extending  longitudinally  the 
frame,  is  secured  a  conductor  c3,  comprising  a  sheet  or  plate  of 
suitable  metal.  Resting  in  said  frame  and  upon  said  conductors 
c3,  is  a  tray  D,  comprising  as  shown,  side  rails  d  parallel  with  the 
side  rails  c,  of  the  frame,  and  an  end  rail  d\  The  bottom  of  said 
tray  comprises  a  sheet  or  sheets  of  metal  d2,  conveniently  copper, 
which,  to  limit  the  exposed  cathode  surface,  may  be  lined  on  the 
upper  side  with  insulating  material  d3,  through  which  project  me- 
tallic pins  d*.  These  are  shown  as  rivets,  rigidly  secured  in  the 
sheet  metal  bottom  of  the  tray  and  the  heads  of  which  protrude 
above  the  lining,  but  of  course  a  non-conducting  bottom  may  be 
used  and  straps  or  bars  of  metal  inserted  m  its  upper  surface  and 
connected  with  the  conductors.  Said  tray  is  rigidly  secured  to  the 
side  members  c  of  the  frame  by  means  of  plates  d*,  which  are  bolted 
to  the  rails  c  and  engage  over  the  side  members  d  of  the  tray.  The 
forward  or  receiving  end  of  said  frame  and  tray  are  supported  at 
an  elevation  above  the  discharge  end  For  this  purpose,  as  shown, 
a  bracket  E  is  rigidly  secured  upon  each  of  the  side  walls  of  the 
tank  at  the  front  end  thereof  and  at  its  upper  part  affords  bear- 
ings for  a  transverse  shaft  e,  on  which  are  journaled  jar  bars  E1, 
one  for  each  side  of  the  frame  C  Rigidly  secured  on  the  forward 
end  of  said  frame  approximately  in  almement  with  the  side  rails  c, 
are  forwardly  projecting  arms  or  brackets  c4,  through  the  forward- 
ly  projecting  ends  of  which  extends  a  shaft  e1  which  also  extends 
through  the  lower  ends  of  the  jar  bars 

Journaled  transversely,  on  the  rear  sides  of  the  brackets  E,  at 
the  top  of  the  tank  is  a  driving  shaft  E2  which  is  provided  at  one  end 
with  a  driving  pulley  e2,  adapted  for  engagement  by  a  suitable  driv- 
ing belt  and  at  its  opposite  end  with  a  suitable  pulley  or  sprocket 
wheel  (in  this  instance  shown  as  a  grooved  pulley),  e3,  adapted  to 
drive  an  elevator  to  deliver  the  plated  articles  from  the  machine. 
Rigidly  secured  on  said  driving  shaft  E;'  are  cams  e4  one  opposite 
each  jar  bar  as  the  driving  shaft  rotates,  drawing  the  frame  and 
tray  forwardly,  and  is  shaped  to  afford  a  quick  release  at  the  for- 
ward limit  of  movement  of  the  jar  bar.  For  this  purpose  the  op- 
posite or  release  side  for  said  cam  projection  is  abrupt,  and  to  fur- 


18G  GALVANIZING  AND  TINNING 

ther  effect  quick  release,  the  lower  rear  side  of  each  jar  bar  is  cut 
away  just  below  the  point  of  contact  with  said  cam  so  that  when 
pressed  forwardly  to  its  limit  of  travel,  immediate  and  complete 
release  follows,  permitting  the  jar  bars  with  the  attached  frame 
and  tray  to  swing  longitudinally  the  tank.  As  shown  a  shaft  F, 
extends  transversely  through"  the  tank  and  secured  thereon  are 
strong  pulling  springs  /,  attached  at  their  ends  respectively  to  the 
jar  bars  and  to  said  shaft  and  which  act  to  snap  the  frame  and 
tray  toward  the  rear  after  each  slow  forward  movement.  Pivotally 
engaged  on  said  shaft  F  is  the  receiving  chute  fl,  the  upper  end  of 
which  rests  on  the  periphery  of  said  cams  and  is  somewhat  wider 
than  the  frame  and  tray.  The  lower  end  thereof  projects  over  the 
tray  and  tapers  to  slightly  less  than  the  width  of  the  tray  to  insure 
the  delivery  of  the  articles  to  be  plated  across  the  entire  width  of 
the  tray.  As  shown  a  strong  pulling  spring  /3  is  secured  on  the  end 
of  said  chute  above  the  cams  and  extends  obliquely  downward  and 
is  attached  to  the  end  of  the  tank  as  shown  in  Figs.  85  and  86,  thus 
holding  the  upper  end  of  the  chute  firmly  on  the  cams.  Said  cams 
act  to  rock  said  chute  on  its  shaft  F,  and  as  the  projections  e5,  on 
the  cams  pass  from  beneath  the  chute,  the  spring  /3  pulls  the  end 
thereof  down  upon  the  cams  constantly,  jarring  the  chute  and  spill- 
ing the  contents  into  the  tray. 

Eigidly  secured  on  the  under  side  of  the  frame  C  are  metallic 
shoes  c6  which  bear  on  the  shaft  B  and  are  of  a  length  to  permit 
the  longitudinal  reciprocation  of  the  frame  and  tray  before  de- 
scribed and  are  conveniently  provided  at  their  front  ends  with  hooks 
c1,  which  extend  beneath  the  shaft  B.  Butting  blocks  G  are  bolted 
one  on  each  side  of  the  tank  and  projecting  inwardly  into  position 
to  afford  stops  for  the  frame  and  tray  at  the  rearward  limit  of  move- 
ment. The  frame  rails  c  are  each  provided  with  a  stop  g  bolted 
on  its  rear  end  in  position  to  abut  the  butting  block  G  at  the  rear- 
ward limit  of  movement  to  suddenly  stop  the  frame  and  tray  when 
snapped  back  by  the  springs. 

Journaled  in  suitable  brackets  H  on  the  rear  end  of  the  tank  is 
a  shaft  h,  having  on  its  outer  end  a  grooved  pulley  /i1,  adapted  to 
receive  the  driving  line  or  belt  h2,  trained  around  the  grooved  pul- 
ley e3  on  the  driving  shaft  E2.  Journaled  transversely  in  the  tank 
near  the  bottom  thereof  and  parallel  the  shafts  h  is  a  shaft  H1,  and 
trained  about  said  shafts  h  and  H1  is  a  conveyer  belt  h3  having 
buckets  /z4  rigidly  secured  thereon  by  riveting  or  other  suitable 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  187 

means.  Each  of  said  buckets  is  perforated  in  its  bottom  to  permit 
the  escape  of  the  electrolyte  and  may  be  constructed  of  sheet  metal, 
fiber  or  any  suitable  material. 

Journaled  on  the  shaft  B  is  a  discharge  chute  I,  at  the  inner  or 
receiving  end  of  which  is  provided  as  shown  a  strap  of  metal  i,  which 
extends  around  the  bottom  and  sides  thereof  and  is  apertured  to 
receive  and  pivotally  engage  on  said  shaft  B.  The  discharge  end 
of  said  chute  I  extends  into  position  to  be  successively  engaged  by 
the  buckets  /i4,  on  the  elevator.  As  the  elevator  is  slowly  driven 
by  the  belt  h2  the  discharge  end  of  said  chute  is  slowly  lifted  until 
the  chute  is  about  horizontal,  at  which  point  it  slips  off  the  bucket 
and  falls  until  engaged  to  be  again  lifted  by  the  next  succeeding 
bucket,  thereby  jarring  its  contents  into  the  buckets  of  the  elevator 
from  whence  they  are  of  course  delivered  from  the  tank. 

As  shown,  conducting  cables  B-  are  secured  on  said  conducting 
shaft  B  and  are  electrically  connected  with  the  metallic  conductor 
c3  in  the  frame,  or  if  desired  may  be  connected  immediately  with 
the  metallic  bottom  of  the  tray. 

Extending  longitudinally  along  the  top  of  the  tank  on  one  of  the 
side  walls  is  a  conductor  k,  and  as  shown,  consisting  of  a  flat  strap 
or  plate  of  metal,  and  hinged  on  one  of  said  side  walls  are  support- 
ing bars  K  for  the  anodes  These  as  shown  in  Figs.  85  and  86  are 
bars  of  wood  or  any  suitable  material,  each  having  on  the  under 
side  thereof  a  bus  bar  comprising  a  strap  of  suitable  conducting 
material  k1  which  rests  on  the  strap  A-,  adjacent  the  hinge,  and  at 
the  opposite  side  of  the  tank  rests  on  a  similar  conductor  k3.  Said 
conductors  k — k-  are  electrically  connected  by  means  of  a  bus  bar 
P  which  extends  across  the  tank  and  with  which  one  of  the  leads 
from  the  source  of  current  is  connected.  Suitable  bolts  k*  extend 
through  said  bar  K  and  bus  bars  k1  and  rigidly  engaged  thereto 
at  the  lower  ends  thereof  transversely  the  cathode  tray  are  the 
anodes  K1,  which  may  be  of"  any  desired  number  and  are  conven- 
iently of  the  metal  it  is  desired  to  plate  upon  the  articles  treated. 
Said  supporting  bolts  fc4  are  progressively  longer  toward  the  rear 
end  of  the  tank  so  that  said  anodes  are  all  supported  at  the  same 
distance  above  the  tray. 

From  the  construction  described  it  is  obvious  that  any  of  said 
supporting  bars  K  with  its  anode  K1  may  be  swung  upwardly  out 
of  the  electrolyte  for  adjustment  or  renewal  of  the  anode  or  to 
reduce  the  plating  surface  and  control  the  current  density.  This, 


188  GALVANIZING  AND  TINNING 

of  course,  breaks  the  circuit  through  such  bus  bars  without  disturb- 
ing the  other  anodes  or  interfering  with  the  operation  of  the  ap- 
paratus and  affords  an  important  means  for  regulating  the  opera- 
tion. To  insure  a  perfect  contact  when  in  operation  special  forms 
of  construction  are  frequently  used  For  this  the  free  end  of 
said  bar  K  is  provided  with  a  metallic  contact  piece  Jc5  rigidly  bolted 
thereto  and  flanged  under  the  same  to  engage  the  bus  bar  k1  and 
provided  with  a  longitudinally  extending  vertically  set  web  or  knife 
fc6.  This  engages  wedgingly  between  contact  plates  A-7,  which  are 
integrally  connected  with  a  base  member  ks  bolted  or  otherwise 
secured  to  the  conductor  fc2. 

Operation  of  the  Meaker  Machine 

The  operation  is  as  follows:  Sufficient  of  the  electrolyte  having 
been  placed  in  the  tank  A  to  submerge  the  tray  and  the  anodes,  the 
articles  to  be  plated  are  delivered  into  the  tray  slowly  by  means  of 
a  chute  f1  and  the  current  is  turned  on,  and  the  driving  shaft  ac- 
tuated from  any  suitable  source  of  power.  The  rotation  of  said 
shaft  with  its  cams  serves  successively  to  elevate  and  to  drop  the 
forward  end  of  the  chute  /l  upon  the  cam,  the  spring,  of  course, 
pulling  the  end  down  with  considerable  force  upon  the  lower  por- 
tion of  the  cam  and  jarring  the  articles  into  the  tray.  The  cams 
also  press  the  jar  bars  forwardly  until  the  projection  e5  passes  the 
contact  points  on  the  jar  bars,  whereupon  the  springs  /  pull  the 
jar  bars  with  the  frame  and  tray  supported  thereon  rearwardly  of 
the  tank  with  some  violence  until  stopped  abruptly,  thus  tending  to 
jar  and  deliver  or  roll  the  articles  within  said  tray  toward  the  lower 
or  discharge  end  thereof.  To  facilitate  the  rolling  movement  of  said 
articles  the  bottom  of  said  tray  is  arranged  in  successive  steps  or 
ledges,  and  the  metallic  contacts  whether  pins  or  strips  are  so  dis- 
posed that  the  articles  being  treated  are  at  all  times  in  contact  with 
one  or  more  thereof.  The  elevator  is  driven  continuously  from  the 
driving  shaft  and  as  the  articles  plated  successively  fail  into  the 
chute  I,  they  are  moved  rearwardly  into  the  buckets  by  the  move- 
ment of  said  chute,  the  rear  end  of  which  is  raised  slowly  on  one 
elevator  bucket  to  approximately  horizontal  position  when  the 
bucket  passes  from  beneath  the  same  permitting  the  end  of  the  chute 
to  drop  upon  the  next  bucket,  and  below  horizontal,  thus  jarring 
the  articles  rearwardly  on  said  chute  and  into  the  elevator. 

Of  course,  overlapping  metallic  plates  D2  of  copper  or  other 


WaUace  Q.  Imhoff 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  189 

suitable  metal  either  with  or  without  its  surface  covered  or  partly 
covered  with  insulating  material,  may  be  employed  for  the  bottom 
of  the  tray  and  in  either  case  after  the  cathode  surface  or  surfaces 
have  accumulated  a  considerable  coating  of  the  plating  metal  the 
cathodes  may  be  removed  and  fresh  plates  substituted  and  the 
plates  so  coated  or  partly  coated  may  be  utilized  as  anodes  until 
the  surplus  material  has  plated  off.  The  plates  if  so  used,  are  of 
course  provided  with  an  aperture  at  each  end  which  is  covered  by 
the  side  rails  d  of  the  tray  when  used  as  cathodes,  but  which  receive 
the  supporting  rods  A'4  when  used  as  anodes.  In  this  way  all  the 
plating  metal  is  utilized  and  inconvenience  and  loss  from  the  accu- 
mulation of  the  plating  metal  upon  the  cathodes  is  avoided. 

The  anodes  in  the  construction  described  are  capable  of  being 
removed  independently  from  the  electrolyte  and  any  or  all  of  the 
same  may  be  swung  upwardly,  each  bus  bar  breaking  the  circuit  for 
its  anode,  when  lifted.  This  enables  the  plating  surface  and  current 
density  to  be  at  all  times  perfectly  controlled  and  together  with 
the  construction  of  the  cathode  elements  greatly  economizes  in 
current  and  material. 

There  are  also  special  devices  on  the  market  for  special  classes 
of  goods,  such  as  tubes,  sheets,  wire  and  wire  nettings,  etc. 

Hanson  and  Van  Winkle  Pipe  and  Tube  Galvanizing 
Machine 

Considerable  ingenuity  has  been  displayed  in  adapting  mechan- 
ical means  to  the  handling  of  large  quantities  of  pipe  at  an  ex- 
tremely low  cost.  The.  plant  for  work  of  this  kind  consists  of  the 
dynamo,  a  series  of  large  circular  cypress  and  iron  tanks  twelve 
or  more  feet  in  depth,  which  are  arranged  in  a  concrete  pit,  only 
a  few  feet  of  each  tank  being  above  the  floor  level.  The  pit  is 
of  sufficient  size  to  contain  the  number  of  cleaning  and  depositing 
tanks  necessary  and  still  afford  ample  room  for  wiring,  connec- 
tions, repairs,  etc. 

The  work  is  conveyed  on  large  racks  holding  from  100  to  150 
lengths  of  conduit.  An  electric  trolley  carries  the  racks  and  their 
load  from  one  tank  to  the  next,  finally  placing  the  work  pickled 
and  cleaned  in  the  galvanizing  vat,  where  electrical  connection  is 
made  and  the  necessary  amount  of  zinc  deposited.  The  work 
never  leaves  the  rack  from  the  time  it  is  first  placed  in  its  raw 


100 


GALVANIZING  AND  TINNING 


ELECTRO-GALVAXIZIXG  PLAXT  AXD  EQUIPMENT  191 

state  on  the  carrier  until  it  is  delivered  to  the  stock  room  in  a 
imished  condition. 

The  Potthoff  Tube  Galvanizing  Machine 

Figs.  89,  90  and  91  show  a  plating  device  particularly  adapted 
for  the  plating  of  bars  or  pipes.  The  machine  is  constructed  of 
a  large  tank  of  considerable  length  and  the  width  governed  by  the 
length  of  the  goods.  The  tank  is  provided  with  two  or  more  metal- 
lic bars  carrying  the  negative  current  on  which  the  tubes  rest  and 


FIG.  89.   POTTHOFF  TUBE  GALVANIZING  MACHINE 

travel.  Above  the  tank  and  electrolyte  is  a  special  conveyor  mounted 
and  so  constructed  keeping  the  tubes  separate  and  moving  same 
slowly  through  the  electrolyte.  The  tubes  are  automatically  dis- 
charged from  this  apparatus  into  a  hot-water  tank.  This  is  a 
patent  of  Louis  Pottholf,  of  ih-j  United  States  Electro  Galvanizing 
Co.  of  Brooklyn.  X.  Y. 

1,  in  Fig.  90,  represents  a  suitable  tank  or  receptacle  having 
mounted  thereon  the  framework  2,  carrying  hangers  3,  in  which 
are  shafts  4  4.  Mounted  on  the  shafts  4  are  sprocket-wheels  5  5, 
around  which  run  chains  or  belts  6  6.  Mounted  at  intervals  on 
the  chains  are  pins  T,  which  engage  the  work  and  move  it  through 
the  solution.  The  pins  7  may  be  made  of  wood  or  other  non- 
conducting material  and  so  shaped  as  to  cause  round  work,  such 
as  tubes,  to  roll  when  engaged  by  them.  It  will  be  obvious  that 
instead  of  one  long  chain  extending  the  length  of  the  tank  a 


15)2 


GALVANIZING  AND  TINNING 


plurality  of  chains  may  be  used  to  avoid  the  objection  due  to  sag- 
ging of  a  long  chain,  this  arrangement  also  serving  to  change  the 
points  of  contact  between  the  pins  and  the  work  on  account  of 
their  different  alinement.  The  pin  is  straight-edged  on  both  sides, 
instead  of  straight  on  one  side  and  curved  on  the  other,  and  has 
two  separated  prongs,  so  that  in  cases  where  the  work  is  short  a 
single  chain  may  be  used  instead  of  two  chains.  The  pins  are 


FIG.  90.   LONGITUDINAL  SECTION  or  POTTHOFF  TUBE  MACHINE 


PlG.  91.    TRANSVERSE  SECTION  OF  POTTHOFF  TUBE  MACHINE 

made  readily  detachable,  so  that  one  may  be  substituted  for  an- 
other. In  order  to  change  the  points  of  contact  between  the  pins 
and  the  work,  fixed  cams  or  inclines  8  are  provided,  against  which 
the  work  will  strike  and  be  moved  thereby  tranversely,  so  as  to 
contact  with  both  the  pins  and  the  cathode-terminals  at  different 
points. 

9  9  represent  the  anodes,  which  are  composed  of  the  metal  to 
be  deposited  and  disposed  so  that  the  current  may  pass  from  them 
through  the  solution  to  the  work  and  thence  out  through  the 
conductor-bars  1 1 ,  which  are  covered  with  insulation,  except  where 
the  work  contacts.  The  anodes  may  be  supported  by  hooks  10, 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  193 

which  are  connected  with  supply-mains.  These  cathode-terminals 
11  form  a  track  or  guide  which  is  inclined  to  the  chains  6,  so 
that  as  the  work  is  moved  along  by  the  pins  the  points  of  con- 
tact with  the  cathode-terminal  continually  change,  thus  permitting 
entire  covering  of  the  work  with  deposited  metal.  The  work  is 
fed  in  at  the  left  and  is  supported  by  the  pins  7  against  the  guide- 
bars  11  until  it  gets  to  the  horizontal  portion  and  is  thereafter 
merely  moved  along  by  the  pins,  being  supported  by  the  bars. 
Round  work  is  rolled  along  by  the  pins  as  the  chain  moves;  but 
work  of  angular  shape  will  slide,  and  in  order  to  insure  that  all 
the  contacts  with  the  bars  11  will  not  be  on  one  side  one  or  more 
inclines  and  depressions  12  13  are  provided  in  the  cathode,  which 
will  cause  the  work  to  turn  over  as  it  is  moved  along  by  the  pins. 
At  the  opposite  end  the  work  is  fed  out  onto  a  table  or  other 
receptacle  14.  It  will  be  understood  that  the  bars  11  are  to  be 
connected  with  negative  mains.  The  discharge  end  of  one  bar  is 
higher  than  that  of  the  other,  so  that  the  electrolyte  will  be  auto- 
matically discharged  from  the  work  before  it  falls  on  the  table. 

In  order  to  deposit  on  the  interior  of  tubes,  it  is  necessary  to 
pass  an  anode  20  through  the  tube  27  without  having  it  contact 
therewith.  If  an  anode  be  covered  with  a  meshed  fabric  29,  such 
as  burlap,  or  cocoa-matting,  the  passage  of  metal  therethrough  is 
not  retarded  and  burning,  due  to  contact  between  the  anode  and 
the  work,  prevented.  As  the  inside  anode  is  gradually  dissolved, 
the  wrapping  becomes  more  loose,  thus  permitting  free  movement 
of  the  anode  inside  of  the  wrapping  as  the  work  moves  along. 

If  desired,  the  current  may  be  conducted  to  the  inside  anode 
from  the  outside  anode  through  the  solution  without  using  the 
track  21.  As  long  as  the  inside  anode  and  the  tube  are  of  dif- 
ferent polarities  no  deposit  will  be  made  on  the  inside  anode  by 
any  positive  current  which  it  may  receive  from  any  positive  con- 
ductor, and  this  condition  will  be  maintained  as  long  as  the  voltage 
is  not  so  high  as  to  cause  the  current  to  jump  across  from  the 
inside  anode  20  to  the  tube  through  the  wrapping.  The  thickness 
of  the  wrapping  must  therefore  be  proportioned  according  to  the 
voltage  which  is  to  be  used.  Under  some  circumstances  it  will  be 
desirable  to  use  a  high  voltage  and  thick  wrapping  without  the 
track,  and  in  other  cases  to  use  a  low  voltage  and  thin  wrapping 
in  connection  with  the  track  21,  connected  with  the  positive  mains. 

It  will  be  obvious  that  the  use  of  the  inside  anode  is  not  re- 


J94  GALVANIZING  AND  TINNING 

stricted  to  round  work,  as  work  of  other  shapes  may  be  equally 
well  galvanized,  and  it  will  also  be  seen  that  partial  tubes — such 
as  angles,  etc. — may  be  galvanized  on  both  sides  by  using  appro- 
priately shaped  anodes. 

22  is  a  stiffening-rod,  composed,  preferably,  of  wood,  which  passes 
through  the  inside  anode  20  and  prevents  its  breaking  when  a 
considerable  amount  has  been  dissolved  off.     For  instance,  where 
anodes  of  zinc  are  used  this  stiffening-rod  becomes  quite  essential, 
because  of  the  brittleness  of  zinc. 

23  represents  rotary  paddles  or  propellers  which  may  be  driven 
from  the  shaft  4  by  a  belt  2-i  to  force  the  electrolyte  to  circulate 
through  tubular  work  as  it  is  moved  along. 

In  galvanizing  small  pipes  it  has  been  found  that  air  sometimes 
becomes  trapped  in  the  tube  and  the  meshes  of  the  fabric,  espe- 
cially if  the  tube  is  carried  into  the  electrolyte  horizontally,  which 
permits  the  electrolyte  to  rush  in  at  both  ends  simultaneously.  By 
feeding  one  end  of  the  tube  in  before  the  other  the  contained  air 
can  escape  from  the  end  not  immersed,  and  thus  prevent  the  trap- 
ping of  air  within  the  tube.  This  can  be  accomplished  by  mak- 
ing the  straight  backs  of  the  pins  higher  on  one  chain  than  on  the 
other,  as  at  26,  so  as  to  incline  the  tube,  and  also  by  setting  the 
pins  of  one  chain  slightly  in  advance  of  the  other,  the  sprockets 
being  provided  with  set-screws  for  the  purpose.  It  will  be  seen 
that  the  tube  can  be  fed  in  in  an  inclined  position  and  yet  be 
carried  through  the  tank  in  a  straight  line,  because  the  tube  comes 
in  on  the  back  edges  of  the  pins  and  is  fed  along  by  the  front 
edges.  By  setting  the  pins  of  one  chain  in  advance  of  those  of 
the  other,  the  electrolyte  will  be  permitted  to  run  out  of  the  tubes 
before  they  are  discharged,  or,  as  before  stated,  one  bar  can  be 
made  higher  than  the  other  at  each  end. 

The  King  Continuous  Wire  Cloth  Machine 

Continuous  methods  for  handling  hoop  iron,  corset  steel, 
cartridge  steel  and  wire  netting  for  window  screens  have 
been  devised  which  greatly  facilitate  the  turning  out  of  quan- 
tities of  work  daily  at  a  minimum  cost.  In  equipment  of  this 
kind  the  work  is  placed  on  large  rolls  at  the  beginning  end  of  the 
process  (Fig.  92)  and  is  carried  through  the  various  pickling, 
cleaning  and  galvanizing  operations  continuously  to  another  set 
of  rolls  at  the  end  of  the  operation,  where  the  work  is  'reeled  up 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT 


:  <)G  GALVANIZING  AND  TINNING 

iii  a  finished  condition,  impulse  being  imparted  to  the  various 
rollers  by  mechanical  means  so  the  work  is  moved  evenly  through 
the  various  tanks.  Plants  of  this  character  in  the  United  States 
are  at  present  turning  out  over  100,000,000  sq.  ft.  of  galvanized 
wire  cloth  each  year. 

The  reference-character  1,  in  Figs.  93  and  94,  indicates  any 
desirable  form  of  supporting  frame-work  or  foundation  upon  which 
the  various  apparatus  may  be  arranged. 


FIG.  93.    RIDE  ELEVATION  OF  KING'S  WIRE  CLOTH  MACHINE 


FIG.   94.    PLAN   OF   KING'S   WIRE   CLOTH   MACHINE 

The  reference-character  2  indicates  the  standards  between  which 
are  mounted  the  shafts  3,  bearing  the  reels  or  drums  ±  upon  which 
the  long  lengths  of  metallic  material  5  are  carried.  The  said 
lengths  of  metallic  material  5  are  first  carried  into  a  cleaning  ap- 
paratus, which  comprises  a  metallic  tank  6  provided  with  a  bind- 
ing-post 7  to  which  is  attached  a  wire  8  of  an  electrical  circuit. 
Arranged  within  said  tank  G  is  a  frame-work  9  which  is  provided 
with  bearings  10,  in  which  are  suitably  mounted  rollers  11.  The 
said  frame-work  is  supported  upon  the  bottom  of  the  tank  6  by 
means  of  insulating  blocks  12.  The  said  tank  6  is  filled  with  a 
solution  of  potash  which  is  kept  hot  by  means  of  a  steam-coil  13, 
or  the  like,  arranged  beneath  said  tank.  This  potash  solution 
cleanses  the  metallic  material  as  it  is  passed  therethrough,  from 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT          197 

all  grease  and  foreign  material  which  may  cling  to  the  surface 
of  the  same.  The  metallic  material  is  drawn  from  the  reels  or 
drums  4  and  passed  under  the  rollers  11  so  as  to  submerge  the 
same  in  the  potash  solution,  and  upon  emerging  from  said  solution 
of  potash,  the  strips  of  metallic  material  pass  over  a  contact-rod 
14  mounted  rotatably  between  standards  15.  The  said  contact- 
rod  14  is  arranged  in  the  electrical  circuit,  by  means  of  a  bind- 
ing-post 16,  one  end  of  which  carries  a  brush  17  which  rides  in 
contact  with  said  contact-rod  14,  and  the  said  binding-post  being 
connected  with  an  electrical  conductor  18,  whereby  the  circuit  is 
established  and  completed  through  the  tank  6,  the  potash-solution 
to  the  strips  5  in  contact  with  the  contact  rod  14,  and  through  the 
brush  17  and  binding-post  16  to  said  conductor  18.  Arranged 
adjacent  to  said  tank  6  is  a  tank  19  and  rotatably  arranged  in  the 
interior  thereof  is  a  guide-roller  20.  The  tank  19  is  filled  with 
cold  water  and  the  metallic  material  is  carried  from  said  contact- 
rod  14.  beneath  said  guide-roller  20,  so  as  to  submerge  the  same 
in  the  said  water,  whereby  the  potash-solution  clinging  thereto  Is 
rinsed  or  washed  off,  as  will  be  clearly  evident.  Mounted  between 
a  pair  of  standards  21  is  a  shaft  22  upon  which  is  secured  a  driv- 
ing or  conveying  roller  23,  over  which  the  metallic  material  5  is 
carried  after  emerging  from  the  water  in  said  tank  19.  Arranged 
adjacent  to  said  tank  19  is  a  tank  24  also  provided  with  an  inter- 
nally arranged  guide-roller  25,  said  tank  24  being  filled  with  a 
pickling  solution  for  the  purpose  of  removing  any  scale  or  the  like, 
which,  in  cases  where  the  metallic  material  to  be  plated  has  been 
annealed,  may  cling  to  the  surface  of  said  metallic  material.  The 
metallic  material  is  carried  from  said  driving  or  conveying  roller 
23  beneath  the  said  guide-roller  25,  so  as  to  submerge  the  same  in 
the  said  pickling  solution. 

Mounted  between  a  pair  of  standards  26  is  a  shaft  27  upon 
which  is  secured  a  driving  or  conveying  roller  28,  over  which  the 
metallic  material  5  is  carried  after  emerging  from  the  said  pickling 
solution.  Arranged  adjacent  to  said  tank  24  is  a  tank  29  which  is 
provided  with  an  internally  arranged  guide-roller  30,  said  tank 
29  being  filled  with  cold  water,  and  the  metallic  material  5  is  car- 
ried from  said  driving  or  conveying  roller  28  beneath  said  guide- 
roller  30,  so  as  to  be  submerged  in  the  water,  and  whereby  the 
pickling  solution  clinging  thereto  is  rinsed  or  washed  off  of  the 
same.  Mounted  between  a  pair  of  standards  31  is  a  contact-rod 


198  GALVANIZING  AND  TINNING 

32,  and  arranged  upon  one  of  said  standards  31  is  a  binding-post 

33,  i?  which  is  secured  one  end  of  an  electrical  conductor  34  of  an 
electrical  circuit.     Connected  with  said  binding-post  is  a  brush- 
liolder  35  in  which  is  arranged  a  suitable  brush  36,  the  free  end  of 
which  is  adapted  to  be  maintained  in  electrical  contact  with  said 
contact-rod  32.    The  strips  of  metallic  material  5  upon  emerging 
from  said  cold  water  tank  29  pass  over  said  contact-rod  32  and  are 
thus  brought  in  electrical  contact  therewith.    Arranged  adjacent  to 
said  tank  29  is  another  tank  37  which  is  provided  with  an  inter- 
nally arranged   guide-roller  38.     This  tank   37  is  filled  with   a 
solution  of  copper  or  other  salts  so  as  to  provide  a  copper  or  other 
suitable  bath,  and  the  metallic  material  5  is  carried  from  said 
contact-rod  32  beneath  said  guide-roller  38,  so  as  to  submerge  the 
same  in  the  said  bath.     Secured  upon  the  upper  edges  of  the  sides 
of  said  tank  37  are  contact-rods  39  which  are  provided  with  bind- 
ing-posts 40,  a  connecting  conductor  41  being  arranged  between 
said  binding-posts  40.     One  of  said  conductors  is  connected  with 
an  electrical  conductor  42  of  an  electrical  circuit.  Suspended  from 
said  contact-rods  39,  by  means  of  suitable  hangers,  as  43,  are  a 
plurality    of  anodes   44,   so   arranged  that   one   group   is  placed 
adjacent  to  the  upper  surfaces  of  said  strips  of  metallic-material  5, 
and  the  other  group  is  arranged  adjacent  to  the  under  surfaces  of 
said  strips  of  metallic  material  5.     Mounted  between  a  pair  of 
standards  45  is  a  shaft  46  upon  which  is  secured  a  driving  or  con- 
veying roller  47,  over  which  the  said  strips  of  metallic  material  5 
are  carried  after  emerging  from  the  said  copper-bath;  and,  ad- 
jacent .to  said  tank  37  is  another  tank  48  which  is  provided  with 
an  internally  arranged  guide-roller  49.     This  tank  48  is  filled 
with  cold  water  and  the  strips  of  metallic  material  5  are  carried 
from  said  driving  or  conveying  roller  47  beneath  said  guide-roller 
49  so  as  to  be  submerged  in  the  said  water,  whereby  any  portion 
of  the  solution  still  clinging  thereto  may  be  rinsed  or  washed 
off.    Mounted  between  a  pair  of  standards  50  is  a  shaft  51  upon 
which  is  secured  a   driving  or  conveying  roller   52,   over  which 
the  said  strips  of  metallic  material   5   are   carried  after  emerg- 
ing  from   the   cold   water   tank   48,    and   adjacent   to    said    cold 
water  tank  48  is  a  long  trough-like  plating-tank  53,  adapted  to 
be  filled  with  any  desirable  electroplating  solution.     This  tank 
53  is  provided  at  each  end  with  internally  arranged  guide-rollers 
54,  and  suitably  disposed  within  said  plating-tank   53,  between 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  199 

the  said  guide- rollers  ol-  and  on  a  slightly  lower  plane  than  said 
guide-rollers  51,  are  a  plurality  of  supporting  or  carrying  rollers 
55.  Mounted  between  a  pair  of  standards  56  is  a  contact-rod  57. 
Secured  to  the  upper  edge  of  one  side  of  said  tank  53  is  a  sup- 
porting bracket  58,  in  the  free  end  of  which  is  arranged  a  binding- 
post  59,  to  which  is  secured  one  end  of  an  electrical  conductor  60 
of  an  electrical  circuit.  Connected  with  said  binding-post  59  is 
a  brush-holder  61  in  which  is  arranged  a  brush  62,  the  free  end 
of  which  is  adapted  to  be  maintained  in  electrical  contact  with 
said  contact-rod  57. 

Secured  upon  one  end  of  said  plating-tank  53  are  a  pair  of 
standards  63  in  each  of  which  are  arranged  a  pair  of  sliding 
journal-boxes  64  Journaled  in  said  boxes  64  are  shafts  67,  and 
suitably  mounted  or  secured  upon  said  shafts  are  resilient,  rollers 
G6.  Secured  to  the  outer  ends  of  said  shafts  67  are  gears  65 
which  arc  in  mesh  with  each  other  and  are  adapted  to  drive 
the  said  rollers  in  opposite  directions.  One  of  said  shafts  67 
is  provided  upon  one  end  with  a  driving  wheel  68  of  large  diam- 
eter, said  driving-wheel  68  being  connected  by  means  of  a  belt 
G'J,  or  the  like,  with  a  small  pulley  70  on  a  main  power  shaft  71. 
The  said  strips  of  metallic  material  5  are  carried  from  said 
.iriving  or  conveying  roller  52,  beneath  one  of  said  guide-rollers 
54.  and  then  extend  longitudinally  through  said  plating-tank  53, 
being  supported  by  said  supporting  or  carrying  rollers  55  and 
submerged  in  said  electroplating  solution,  said  metallic  material 
then  extending  beneath  the  other  of  said  guide-rollers  54,  at  the 
opposite  end  of  said  tank  53,  emerging  from  the  said  electro- 
plating fluid  or  solution  and  then  passing  over  said  con  tact- rod  57, 
oeing  in  electrical  contact  therewith,  and  thence  through  or  be- 
tween the  said  resilient  rollers  66.  Secured  upon  the  upper  edge- 
surfaces  of  the  sides  of  said  plating-tank  53  are  contact-rods  72, 
provided  with  binding-posts  73,  a  connecting  conductor  74  being 
secured  to  and  joining  in  electrical  circuit  both  of  said  contact- 
rods  72.  one  of  said  binding-posts  being  connected  with  an  elec- 
trical conductor  75  of  an  electrical  circuit.  Suspended  from  said 
contact-rods  72,  by  means  of  hangers  76,  are  a  plurality  of  anodes 
77,  which  are  arranged  so  as  to  be  grouped  between  the  said 
£uide-rollers  54  and  each  of  the  said  supporting  or  carrying  rol- 
lers 55.  The  said  anodes  77  are  further  arranged  in  such  a. 
manner  so  that  some  of  the  same  extend  laterally  across  sa:d 


200  GALVANIZING  AND  TINNING 

plating-tank  53,  adjacent  to  the  upper  surfaces  of  said  strips 
of  metallic  material  5,  and  other  anodes  extending  laterally  across 
said  tank,  adjacent  to  the  under  surfaces  of  said  strips  of  metallic 
material  5.  Arranged  adjacent  to  said  plating-tank  53  is  a  metal- 
lic-tank 78,  which  is  provided  with  frame-members  79  between 
which  are  mounted  an  internal  guide-roller  80  and  an  outer  guide- 
roller  81.  This  tank  78  is  adapted  to  be  filled  with  hot  water, 
which  is  kept  hot  by  means  of  a  steam-coil  82,  or  any  other  de- 
sirable heating  unit,  said  coil  being  arranged  beneath  the  bottom 
of  said  tank  78.  V'i7?ie  strips  of  metallic  material  pass  from  said 
resilient  rollers  66,  beneath  the  said  internally  arranged  guide- 
roller  80,  so  as  to  submerge  the  said  strips  of  metallic  material 
5  therein,  for  the  purpose  of  thoroughly  cleansing  and  washing  off 
of  the  same  any  of  the  electroplating  solution  still  clinging 
thereto,  the  said  strips  5  then  being  carried  over  said  outer  guide- 
roller  81,  and  thence  through  the  hood  83  of  a  drying  apparatus, 
said  drying  apparatus  being  arranged  adjacent  to  the  end  of  said 
metallic  tank  78.  This  drying  apparatus  comprises  a  box-like 
compartment  84,  supported  upon  a  frame-work  or  legs  85,  and 
arranged  therein  is  a  steam-coil  86,  or  any  other  desirable  heat- 
ing unit.  Connected  with  the  compartment  84  and  arranged  above 
said  steam-coil  86  is  a  perforated  plate  87,  over  which  is  ar- 
ranged the  said  hood  83,  tho  same  being  provided  with  openings 
88  at  each  end  for  the  entrance  and  exit  of  said  strips  5.,  the 
said  hood  83  forming  a  drying  chamber  89. 

Mounted  between  a  pair  of  standards  90,  which  are  located 
adjacent  to  the  drying  apparatus,  is.  a  shaft  91  upon  which  are 
secured  suitable  receiving  reels  or  drums  92,  upon  which  the  said 
strips  of  metallic  material  5  are  rolled  or  wound  after  passing 
through  said  drying  apparatus.  Secured  upon  one  end  of  said 
shaft  is  a  ratchet-wheel  93,  and  pivotally  arranged  upon  said 
shaft,  adjacent  to  said  ratchet-wheel  93,  is  a  vibrator-arm  or  lever 
94,  the  free  end  of  which  is  provided  with  a  stud  to  which  is 
pivotally  connected  a  pawl  95  which  is  adapted  to  engage  with 
the  teeth  of  said  ratchet-wheel  93.  The  means  for  operating  said 
vibrator-rod  or  lever  94  and  the  pawl  95,  to  turn  or  drive  the 
said  ratchet-wheel  93,  comprises  a  crank-shaft  96,  one  end  of 
which  is  pivotally  connected  with  said  vibrator-rod  or  lever  94, 
and  the  other  end  of  which  is  connected  eccentrically  with  the 
side  or  plane-surface  of  a  pulley  97  secured  to  a  main  power- 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  201 

&naft  98.  The  reciprocating  action  of  said  crank-shaft  96,  bj 
means  of  said  vibrator-rod  or  lever  94  and  its  pawl  95  thus  im- 
parts to  said  ratchet-wheel  93  and  the  shaft  91  a  rotary  motion 
as  will  be  clearly  evident.  This  motion  is  slow,  but  very  positive, 
and  assures  the  drawing  of  the  said  metallic  strips  5  through 
the  various  devices  of  the  apparatus  heremabove  described,  and 
it  is  finallv  reeled  or  rolled  in  its  finished  condition  upon  said 
reels  or  drums  92.  To  further  aid  the  drawing  or  passage  or 
said  strips  of  metallic  material  through  the  said  ^various  devices 
of  the  apparatus,  the  said  shafts  22,  27,  46  and "51,  upon  which 
are  mounted  or  secured  the  said  driving  or  conveying  rollers  23, 
28,  47  and  52,  as  well  as  the  various  revolving  contact-rods  14,  32 
and  57,  are  all  provided  with  pulleys  99,  and  are  operatively  con- 
nected with  a  pulley  100  secured  upon  one  of  said  shafts  65,  so 
as  to  pass  the  driving  power  from  one  to  the  other  of  said  shafts 
and  contact-rods  57,  51,  46,  32,  27,  22  and  14,  by  means  of  belt- 
connections  101,  thereby  reducing  the  friction  and  aiding  mate- 
rially in  passing  the  said  metallic-strips  5  through  the  various 
devices  of  the  whole  apparatus. 

From  the  foregoing  description  of  the  novel  plant  for  electro- 
plating extraordinarily  long  lengths  of  metallic  material,  it  will  be 
readily  seen  that  such  material  is  easily  manipulated  for  the  pur- 
pose of  carrying  out  the  various  steps  of  a  perfect  electroplating 
process,  regardless  of  the  length  of  the  material  to  be  plated. 
The  material  is  passed  through  the  various  devices  and  tanks 
of  the  apparatus,  such  as  the  potash-tank,  "the  picklmg-tank,  the 
copper-bath  tank,  and  their  intermediate  cleansing  tanks,  con- 
tinuously without  the  necessity  of  frequent  handling.  As  one 
portion  of  material  is  treated  to  one  step  of  the  process,  it  passes 
on  to  the  next  device,  there  to  be  further  treated,  and  another  por- 
tion follows,  in  sequence,  until  the  plating-tank  is  reached,  where 
the  metal  is  deposited  on  said  material  in  carrying  out  the  actual 
plating  step,  and  then  the  finished  portion  is  drawn  through  the 
resilient  rolls  66  which  squeeze  off  the  solution  from  the  finished 
or  plated  surface.  The  further  cleansing  of  said  finished  or  plated 
surface  is  accomplished  in  the  hot-water  tank,  and  thence  the 
material  passes  to  the  drying  apparatus  and  is  finally  reeled  upon 
the  receiving  reels  or  drums  in  its  finished  or  plated  state.  The 
movement  of  said  metallic  material  through  the  various  apparatus, 
while  it  is  continuous  is  nevertheless  very  slow,  so  that  sufficient 


202  GALVANIZING  AND  TINNING 

time  is  allowed  to  permit  of  the  completion  of  each  preparatory 
step,  as  well  as  of  the  main  plating-step  of  the  electro-plating 
process,  and  each  portion  of  said  metallic  material  is  evenly  and 
perfectly  treated  to  the  final  completion  of  the  said  process. 

The  Root  Wire  Cloth  Machine 

Illustration  95  shows  an  apparatus  for  electro-galvanizing 
wire  cloth.  As  clearly  shown  in  the  illustration,  a  plating  tank 
is  provided  with  metallic  rollers  above  the  electrolyte  and  with 


FIG.  95.    PERSPECTIVE  VIEW  OF  ROOT  WIRE  CLOTH  MACHINE 


wooden  rollers  below  the  electrolyte  and  resting  at  the  bottom  of 
the  t^nk.  Between  each  pair  of  rollers  a  set  of  anodes  is  adjusted. 
By  thfs  construction  a  large  amount  of  cathode  surface  is  exposed 
to  the  anode  surface  in  a  narrow  space.  This  device  is  a  patent 
of  Francis  J.  Root,  of  the  New  York  Wire  Cloth  Company,  New 
York,  N.  Y.  To  make  the  process  of  electro-galvanizing  wire  cloth 
and  similar  articles,  like  wire,  band  iron  and  sheets  a  continuous 
one,  similar  tanks  have  to  be  employed,  for  pickling,  cleaning,  hot 
water,  drying  and  enameling.  One  row  of  goods  is  always  con- 
nected onto  the  next  one. 

The  tank  1  is  made  of  wood  and  is  water-tight  to  hold  any 
suitable  bath  or  solution  which  may  be  desired  during  the  plat- 
ing process.  Within  the  lower  portion  of  the  tank  and  also  above 
the  tank  are  rollers  3  and  4,  which  extend  transversely  thereof. 
The  material,  moved  along  by  suitable  pulling  or  propelling  means, 


ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  203 

enters  the  apparatus,  passes  over  a  roller  in  the  upper  set,  then 
down  into  the  bath  under  a  roller  of  the  lower  set,  out  of  the 
bath  over  another  roller  of  the  upper  set,  and  so  on  in  vertical 
folds  or  loops  through  the  apparatus.  It  will  be  observed  that 
the  rollers  are  in  staggered  arrangement  so  that  those  in  the  lower 
set  are  located  below  the  spaces  between  adjacent  rollers  of  the 
upper  set.  Directly  below  the  rollers  of  the  upper  set  and  above 
the  rollers  of  the  lower  set  are  the  metal  anodes  5  for  providing 
the  plating  material. 

The  lower  rollers  3  are  supported  within  the  tank  by  means  of 
bearings  6  carried  on  the  longitudinal  members  7,  and  the  upper 
rollers  4  are  supported  in  metal  bearings  8  carried  on  the  longi- 
tudinally extending  members  9  and  10,  which  are  held  in  place 
by  the  uprights  10*.  Either  one  or  both  of  the  members  9  may 
be  made  of  a  metal  which  will  readily  conduct  electricity  and,  there- 
fore, can  serve  as  a  "bus  bar"  or  common  electrical-connecting 
means  for  the  upper  rollers  or  cathodes,  all  of  which  are  electrically 
connected  thereto.  This  "bus  bar"  or  common  electrical-connecting 
means  is  connected  to  the  negative  terminal  of  an  electric  circuit, 
the  positive  end  of  which  is  connected  to  the  anodes. 

The  anodes  5  are  supported  in  place  by  and  suspended  from  rods 
11  extending  transversely  across  the  upper  portion  of  the  tank. 
Each  of  these  rods  is  provided  with  a  depending  member  12  lead- 
ing to  another  "bus  bar"  or  common  electrical-connecting  means  13, 
to  which  the  positive  terminal  of  the  electrical  circuit  is  connected. 
The  anodes  are  provided  with  hooks  to  hold  them  in  place,  and 
it  is  obvious  that  one  which  has  been  used  can  readily  be  re- 
placed by  a  new  one  when  desired.  The  anodes  are  arranged 
directly  over  the  lower  rolls  and  beneath  the  upper  rolls,  and  are 
located  within  the  extremities  of  the  body  portion  thereof.  It  is 
apparent  that  said  anodes  are  between  adjacent  vertically  extend- 
ing portions  of  the  folds  or  layers  of  the  work  as  it  passes  through 
the  apparatus,  thereby  bringing  all  portions  of  the  two  broad  sur- 
faces of  the  work  close  thereto,  thus  enabling  a  uniform  deposit  of 
the  coating  substance  upon  the  work  to  be  obtained. 

In  coating  pieces  of  work  like  wire  cloth,  such  as  is  used  for 
ordinary  window  screening  to  keep  out  insects,  this  apparatus  is 
particularly  useful. 

It  will  be  observed  that  the  work  passes  out  of  the  bath  each 
time  it  passes  over  an  upper  roller  and  this  aids  in  breaking  any 


204  GALVANIZING  AND  TINNING 

bubbles  of  gas  which  may  have  been  formed  upon  the  work  and 
also  permits  gas  accumulation  to  pass  off  or  dissipate  into  the 
atmosphere. 

As  the  rollers  in  the  upper  set  are  all  connected  to  an  end  of 
the  electric  circuit,  the  work  passing  thereover  will  also  be  re- 
charged prior  to  being  reintroduced  into  the  bath. 

With  the  upper  rollers  or  guiding  means  located  above  the  bath 
it  will  be  observed  that  the  work  can  be  readily  inspected  at  all 
stages  in  its  passage  through  the  apparatus,  thereby  permitting  the 
apparatus  to  be  operated  and  the  process  to  be  effected  in  the 
most  advantageous  manner. 

All  of  the  rollers  as  shown  are  provided  with  flanges  to  retain 
the  work  in  place  thereupon.  The  work  could,  however,  be  re- 
tained in  place  by  other  means  if  desired.  The  rollers  serve  for 
guiding  the  work  through  the  apparatus  and  also  for  providing 
means  to  conduct  the  electricity  to  the  work  at  several  points  along 
its  path  through  the  apparatus.  When  driven  they  also  serve  as 
means  for  propelling  the  work. 

Schulte  Wire  Galvanizing  Machine 

Figs.  96  and  97  show  an  apparatus  for  similar  purposes, 
and  is  so  constructed  to  allow  the  goods  to  pass  between  hori- 
zontal anodes  on  a  skeleton  framework  through  the  electrolyte. 
Wires,  band  iron,  etc.,  are  from  the  start  fastened  with  a  long, 
flat  clamp  and  arranged  horizontally,  and  through  the  traveling 
cables  or  skeleton  framework  carried  through  the  electrolyte.  After 
this  through  hot  water  and  finally  wound  up  on  spools.  This 
machme  can  also  be  used  for  electro-galvanizing  sheets  by  a  con- 
tinuous method,  also  small  work  in  bulk  quantities  when  placed  in 
a  perforated  basket  and  the  basket  set  on  the  skeleton  framework 
which  travels  through  the  electrolyte.  This  apparatus  is  patented 
by  Louis  Schulte  of  Chicago. 

In  the  tank  A,  filled  with  the  electrolyte  B,  is  arranged  an 
anode  formed  of  the  spaced  anode-plates  C  C1,  between  which 
passes  the  movable  cathode-carrier  D  in  electrical  contact  with 
contact  members  D1,  removably  secured  by  screws  D2  to  the  tank 
A  at  or  near  the  ends  thereof,  as  plainly  indicated  in  the  draw- 
ings. The  anode-plates  C  C1  are  connected  with  the  positive  pole 
of  a  source  of  electrical  energy — such  as  a  battery,  dynamo,  or  the 
like — and  the  contact  members  D1  for  the  cathode-carrier  are  ccn- 


ELECTRO  GALVANIZING  PLANT  AND  EQUIPMENT 


205 


nected  with  the  negative  pole  of  the  said  source  of  electrical  energy. 
The  movable  cathode-carrier  D  is  in  the  form  of  an  endless  skele- 
ton frame  for  supporting  the  articles  and  for  carrying  the  same 
through  the  electrolyte  B  between  the  anode-plates  C  and  C1. 

The  movable  cathode-carrier  D,  as  shown  in  the  drawings,  is 
preferably  formed  of  a  number  of  insulated  endless  cables  D3,  con- 
nected with  each  other  by  insulated  transverse  bars  or  rods  D4, 

FIG.  96.    SIDE  ELEVATION  OF  SCHULTE  WIRE  GALVANIZING  MACHINE 


FIG.  97.    PLAN  OF  SCHULTE  WIRE  GALVANIZING  MACHINE 

spaced  suitable  distances  apart  and  each  provided  with  contact- 
points  D\  having  their  terminals  exposed  through  the  insulating 
material.  Each  contact  member  D1  for  the  cathode-carrier  D 
consists  of  a  frame  D6,  fastened  in  position  on  the  sides  of  the 
tank  by  the  screws  D2,  and  the  said  frame  DG  is  provided  with 
an  inclined  support  I)7,  carrying  springs  Ds,  pressing  the  under 
side  of  contact-plates  IF.  so  as  to  hold  the  latter  in  firm  contact 
at  their  upper  faces  with  the  contact-points  D5,  previously  men- 
tioned, and  arranged  on  the  cross-bars  D4  of  the  skeleton  frame. 

The  insulated  cables  D3  pass  around  rollers  E  and  E1,  journaled 
in  the  sides  of  the  tank  A  at  or  near  the  ends  thereof,  and  on  the 
shaft  E2  of  the  roller  E1  is  secured  a  pulley  E3,  connected  by  a 
belt  E4  with  other  machinery  for  rotating  the  shaft  E2  and  the 
roller  E1  to  cause  the  skeleton  frame  forming  the  movable  cathode- 


206  GALVANIZING  AND  TINNING 

carrier  D  to  travel  through  the  electrolyte  and  between  the  anode- 
plates  C  and  C1. 

The  rollers  E  arid  E1  are  preferably  located  near  the  top  of  the 
tank  A,  and  in  order  to  bring  the  runs  of  the  endless  skeleton 
frame  in  proper  relation  to  the  anode-plates  C  and  C1  supple- 
mentary or  auxiliary  rollers  F  P  are  employed,  journaled  in  the 
sides  of  the  tank  A  and  over  which  passes  the  upper  run  of  the 
endless  skeleton  frame  and  under  which  passes  the  lower  run  of 
the  said  frame,  the  said  runs  being  held  in  engagement  with  the 
rollers  F  F  by  grooved  idlers  or  pulleys  F1,  journaled  in  the  sides 
of  the  tank  A.  Idlers  F2,  similar  to  the  idlers  F1,  engage  the 
outermost  insulated  cables  D3  at  a  point  midway  between  the 
rollers  F  F  to  properly  support  the  runs  between  the  rollers  F  F. 

The  speed  of  the  endless  traveling  skeleton  frame  carrying  the 
articles  is  regulated  to  cause  a  complete  plating  of  the  articles 
on  the  entire  outer  surface  during  the  passage  of  the  article 
through  the  electrolyte  in  the  tank  A. 

If  it  is  desired  to  plate  small  articles,  then  the  same  are  placed 
in  a  metallic  perforate  tray  or  basket  II,  set  on  the  contact-points 
D5  of  the  upper  run  of  the  skeleton  frame  or  fastened  thereto,  so 
that  the  articles  are  passed  through  the  electrolyte  B  and  between 
the  anode-plates  C  and  C1,  the  same  as  the  articles  above  de- 
scribed, and  directly  fastened  to  the  upper  run  of  the  skeleton 
frame.  It  is  understood  that  in  practice  the  large  articles  or  the 
basket  containing  the  small  articles  are  placed  in  position  on  the 
upper  run  of  the  skeleton  frame  at  the  roller  E  and  taken  off  the 
skeleton  frame  at  the  roller  E1. 

By  moving  the  articles  to  be  plated  through  the  electrolyte  the 
hydrogen  is  continually  removed  from  the  surface  of  the  articles 
to  insure  the  formation  of  a  bright  plating  deposit  on  the  articles. 
It  will  also  be  seen  that  by  the  arrangement  described  the  electro- 
lyte is  kept  in  motion  by  the  moving  cathode  to  allow  of  using  a 
very  high  current,  thus  finishing  the  plating  in  a  comparatively 
short  time. 

Electrical  Equipment 

A  dynamo  driven  by  a  revolving  belt  or  motor,  directly  con- 
nected, will  supply  the  necessary  amperes  and  volts  required  to 
deposit  the  zinc  metal  from  the  electrolyte  onto  the  cathode  (goods 
to  be  plated)  and  dissolve  at  the  same  time  an  equivalent  amount 


G.  Imhoff 

ELECTRO-GALVANIZING  PLANT  AND  EQUIPMENT  207 

of  zinc  from  the  zinc  anodes.  A  voltmeter  and  an  ammeter,  as  well 
as  a  rheostat,  are  required  to  control  and  regulate  the  volts  and 
amperes  for  the  different  loads  and  classes  of  work. 

The  generator  supplying  the  current  is  usually  placed  within  40 
or  50  ft.  of  the  galvanizing  bath,  although  this  distance  may  be 
increased  provided  the  conductors  are  also  increased  in  size.  A 
safe  ruling  for  every  30  ft.  added  double  the  size  of  the  conductor. 
First,  30  1";  second,  30  2";  third,  30  -i";  fourth,  30  8".  Great 
advance  has  been  made  in  the  United  States  in  the  manufacture 
of  dynamos  for  deposition  and  it  is  now  possible  to  procure  low- 
voltage  generators  up  to  10,000  amperes  capacity.  Such  generators 
can  handle  1,000  sq.  ft.  of  work  in  a  galvanizing  bath  at  one  time 
or  approximately  16,000  sq.  ft.  of  work  in  a  day  of  10  hours.  This 
is  based  011  using  a  current  of  10  amperes  per  sq.  ft.  and  allowing 
a  30-minute  deposit  and  the  necessary  time  for  filling  empty  tanks. 
In  no  other  form  of  electro-deposition  has  the  demand  been  greater 
for  generators  of  low  tensions  and  high  ampere  capacity  than  in  the 
electro-galvanizing  industry. 

Opinions  differ  as  to  amount  of  voltage  required.  It  is  agreed 
that  low  voltage  gives  softer  and  tougher  deposit",  while  when 
very  heavy  deposits  are  required  low  voltage  is  absolutely  necessary. 

Some  galvanizers  use  2  volts  for  light  work,  while  others  use 
6  volts  on  the  same  class  of  work.  The  latter  saves  time,  but  does 
not  give  as  smooth  a  coating. 

On  big  work  it  is  necessary  to  have  higher  voltage,  because  of 
size  of  tank  and  distance  from  anode,  which  increases  resistance. 

Copper  conductors  should  be  made  of  solid,  flat,  round  or  tubu- 
lar copper  of  size  sufficient  to  carry  required  amperage.  1  sq.  in. 
of  copper  will  carry  1,000  amperes,  and  1  sq.  ft.  of  material  sur- 
face exposed  in  galvanizing  solution  will  require  from  5  to  20 
amperes :  depending  on  voltage  used  and  conductivity  of  solution 
and  anodes. 

Anodes 

The  anode  or  positive  element  from  which  the  metal  is  taken 
is  an  important  item  in  the  electro-galvanizing  process,  its  purity 
determining  to  a  great  measure  the  quality  of  the  work  and  the 
proper  maintenance  of  the  solution.  A  cast  anode  is  to  be  pre- 
ferred, in  shape  elliptical,  round  or  flat.  In  a  cast  anode  the 
structure  is  more  open  and  crystalline  than  in  the  plate  form,  and 


208  GALVANIZING  AND  TINNING 

this  metal  is  readily  disintegrated  under  the  action  of  the  current. 
The  anode  surface  exposed  should  be  one-third  greater  than  the 
cathode  surface. 

Cost  of  Installation 

The  much  slower  rate  at  which  the  zinc  is  deposited  electrically 
makes  the  size  of  the  plant  larger  than  for  the  dipping  process, 
and  the  first  cost  is,  therefore,  greater.  It  should  be  noted,  how- 
ever, that  the  cost  of  one  cubic  foot  of  the  electrolyte  bath  is  but 
a  fraction  of  that  of  the  galvanizing  bath. 

The  solution  tanks  are  usually  made  of  cypress,  3"  or  4"  stock 
with  a  lining  of  a  mixture  of  asphalt  and  pitch,  to  which,  before 
it  is  set,  a  coating  of  hot  white  beach  sand  is  applied,  making  a 
hard,  serviceable  lining.  Tanks  for  pickling  are  usually  made  of 
wood  with  a  lead  lining  and  the  tanks  for  caustics  or  electro-clean- 
ing are  of  iron  or  steel,  arranged  with  steam  coils. 


CHAPTER  XXII 

Preparing  Work  for  Electro-Galvanizing 

MATERIAL  to  be  electro-galvanized  is  cleaned,  preparatory 
to  immersion  in  the  electrolyte,  in  much  the  same  manner 
as  it  is  handled  for  dipping  in  the  hot  process.     A  com- 
prehensive treatment  of  these  methods  is  given  in  Chapters  V  and 
VI  of  this  book. 

While  it  has  frequently  been  stated  that  special  attention  is 
required  and  considerably  more  caution  is  necessary  in  cleaning 
materials  to  be  cold  galvanized,  this  idea  undoubtedly  has  orig- 
inated from  the  fact  that  material  which  has  not  been  thoroughly 
cleaned  can  be  hot  galvanized;  while  the  electrolyte  process  will 
not  act  on  a  surface  that  has  not  been  entirely  freed  from  foreign 
matter,  such  as  oil,  scale,  sand,  etc.  While  it  is  true  that  the 
hot  process  of  galvanizing  will  largely  coat  or  bridge  over  such 
unclean  surfaces,  material  which  is  treated  without  being  properly 
cleaned  will  not  resist  corrosion  so  effectively  as  carefully  pre- 
pared material,  because  the  impurities  set  up  a  corrosive  action 
between  the  basic  metal  and  the  zinc  coating.  In  some  cases  it 
has  been  found  that  the  zinc  coating  would  not  adhere  to  the 
basic  metal  and  the  least  shock  would  loosen  it. 

Knowledge  of  the  effect  of  acids  and  pickles  on  various  forms 
of  iron  and  steel  is  necessary  in  arranging  the  cleaning  and  pick- 
ling baths.  Cold-rolled  and  malleable  iron  are  readily  treated, 
requiring  but  mild  pickling.  Hot-rolled  steel  is  usually  covered 
with  a  hard  scale  which  must  be  pickled  or  otherwise  treated. 
Cast  iron  is  perhaps  the  most  difficult  to  treat  successfully  in  the 
electro-galvanizing  bath.  The  foundry  turns  out  so  many  kinds 
of  castings;  the  quality  depending  upon  the  mixture;  the  char- 
acter of  the  facing  used;  the  temperature  at  which  the  metal  is 
poured ;  the  burning  of  the  sand  into  the  casting ;  the  porosity. 
All  of  these  are  factors  which  make  it  practically  impossible  to 
treat  all  iron  castings  similarly.  In  some  instances  dry  tumblers 
are  used  with  jacks,  the  dust  exhausted  by  a  blower  keeping  the 
castings  clean ;  water  tumblers  are  used  with  other  kinds  of  work. 
If  the  castings  have  received  the  proper  attention  in  the  foundry, 


210  GALVANIZING  AND  TINNING 

tumbling  will  prepare  the  work  so  that  only  a  mild  pickle  need 
be  used. 

Removing  Sand  from  Castings 

It  must  be  remembered  that  while  hydrofluoric  acid  will  remove 
sand  and  scale,  great  care  is  required  in  its  use  and  the  strength 
of  the  acid  should  be  modified.  The  solution  given  below  will 
cause  the  least  danger  to  the  work  if  not  left  in  the  pickle  too  long. 

Hydrofluoric  acid,  30  per  cent 2  parts 

Sulphuric  acid,  66  per  cent 1  part 

Water   8  to  10  parts 

A  hot  pickle  of  140  to  160  deg.  will  work  much  faster  than 
a  cold  one.  It  is  always  best  to  use  the  pickle  as  weak  as  will 
give  the  desired  results  in  a  limited  time.  A  pickle  that  will 
not  properly  treat  the  castings  in  two  or  three  hours  is  a  dan- 
gerous one  to  use. 

During  the  process  of  pickling,  quantities  of  magnetic  oxide  and 
scale  become  detached  and,  if  allowed  to  remain  in  the  pickle,  to  be 
further  acted  upon  by  the  pickle,  will  form  a  serious  source  of  loss. 
A  form  of  electromagnet  has  been  devised  to  remove  this  oxide 
from  the  bath. 

Removing  Oil  or  Grease 

If  the  material  to  be  electro-galvanized  is  of  an  oily  nature, 
that  is,  if  oil  or  grease  has  been  used  in  the  process  of  manu- 
facture, the  first  operation  consists  in  removing  this  foreign  mat- 
ter by  immersion  before  pickling  in  a  bath,  preferably  hot,  of 
caustic  soda  or  a  like  solution  that  will  have  for  its  effect  the 
dissolving  of  the  oil  or  grease.  The  strength  of  the  solution 
and  the  time  required  to  remove  the  oil  or  grease  depends  some- 
what on  the  condition  of  the  material.  If  a  hot,  caustic-soda  .solu- 
tion is  used,  ^  to  ^  Ib.  per  gallon  will  be  found  to  answer  gen- 
eral requirements.  Material  should  be  allowed  to  remain  in  the 
bath  for  a  period  of  5  to  20  minutes.  It  should  then  be  removed 
and  rinsed  in  cold  water  before  being  placed  in  the  pickling  solu- 
tion, as  the  caustic  soda  has  a  tendency  to  neutralize  the  acid. 

Removing  Mill  Scale 

The  removal  of  mill  scale  from  iron  or  steel  is  generally  accom- 
plished by  pickling  the  material  in  a  bath  of  sulphuric  acid,  muri- 


PREPARING  WORK  FOR  ELECTRO-GALVANIZING  21 1 

atic  acid  (hydrochloric  acid)  or  one  of  the  numerous  composi- 
tions for  the  purpose  on  the  market.  The  strength  of  the  solu- 
tion used,  it  will  be  understood,  depends  on  the  thickness  of  the 
scale  to  be  removed  and  the  time  in  which  such  pickling  is  to  be 
done.  One  method  recommended  is  to  place  the  iron  in  a  solu- 
tion of  one  part  hydrochloric  or  sulphuric  acid  to  ten  parts  of 
water  for  a  period  varying  from  ^  hour  to  5  hours,  this  depending 
upon  the  thickness  of  the  scale. 

If  a  sulphuric-acid  bath  is  used,  a  4-per-cent.-by-weight  solution 
of  commercial  acid  will  be  found  to  answer  general  requirements. 
It  should  be  used  hot,  although  a  cold  solution  will  answer  equally 
well  if  the  time  for  pickling  is  sufficient. 

On  some  classes  of  work,  like  chain  grips  for  tires,  it  is  neces- 
sary to  remove  scale,  etc.,  by  first  hanging  in  hot  caustic  soda  to 
remove  oil  and,  after  rinsing,  to  pass  quickly  through  a  dip  of  40  deg. 
nitric  acid,  rinse  again  and  dip  work  in  a  10-per-cent.  muriatic-acid 
solution.  After  being  rinsed  again  the  work  is  ready  for  the  gal- 
vanizing bath  and  will  readily  cover  in  the  deepest  recesses. 

Scratch-Brushing 

When  a  heavy  pickle  is  used,  or  the  work  is  left  too  long  in 
the  acid,  the  surface  of  the  work  shows  a  residue  which  must  be 
removed  before  the  work  is  placed  in  the  electro-galvanizing  bath. 
This  means  hand  work  or  scrubbing,  which  adds  largely  to  the  cost 
of  preparing  the  work. 

Heavy  pieces  of  material  or  of  a  large  surface,  such  as  plates, 
should  also  be  scratch-brushed  after  pickling,  in  order  to  remove 
the  scum  or  residue  and  obtain  a  thoroughly  clean  surface.  In 
many  instances  this  can  also  be  accomplished  easily  and  satis- 
factorily by  placing  the  material  in  an  electro-cleaning  solution 
made  up  for  the  purpose  in  place  of  scratch -brushing.  This  solu- 
tion is  usually  made  from  a  mild  caustic  (about  5  per  cent,  free 
caustic)  solution  G  deg.  B. 

Copper  Flashing 

The  use  of  a  copper  cyanide  strike  as  a  preliminary  to  the  deposit 
of  zinc  has  been  largely  advocated.  Some  discussion  has  arisen  as 
to  the  value  of  the  copper  as  a  resistant  to  corrosion.  It  has  been 
claimed  that  as  zinc  is  electropositive  to  both  copper  and  iron, 
it  affords  protection  to  each  metal.  The  oxidizing  effect  of  the 


212  GALVANIZING  AND  TINNING 

atmosphere  will  in  time  affect  the  zinc  coating  and  change  it  to 
a  zinc  oxide.  Whenever  galvanic  or  electrochemical  action  is  set 
up  by  the  contact  of  iron  and  zinc  and  zinc  in  the  presence  of 
moisture,  it  is  the  zinc  that  is  attacked  and  not  the  iron.  It  is 
claimed  by  some  that  there  is  no  galvanic  action  per  se  in  iron 
coated  with  zinc  and  during  disintegration  the  zinc  affords  pro- 
tection to  the  intermediate  coating  of  copper,  which,  in  turn,  pro- 
tects the  basic  metal.  Others  claim  that  the  use  of  a  copper  flash 
is  bad  practice  because  copper  is  electro  negative  to  both  iron  and 
zinc  and  will,  therefore,  lead  to  more  rapid  destruction  of  both 
these  metals  when  it  is  brought  in  contact  with  them  in  the  pres- 
ence of  the  corroding  medium.  It  further  adds  considerable  to 
the  cost. 

A  dip  copper  lias  been  used  with  some  success  previous  to  gal- 
vanizing and  is  made  as  follows: 

Water 1  gal. 

Sulphuric  acid 1  oz. 

Sulphate  of  copper 1  oz. 

The  work,  after  being  thoroughly  cleaned,  is  immersed  for  a 
few  seconds  in  this  dip  and  rinsed  quickly. 

WThen  the  copper  cyanide  bath  is  used,  the  action  is  similar  to  that 
of  an  electrocleaner.  Gas  is  released  from  the  surface  of  the  work 
by  the  action  of  the  current  and  this  has  a  tendency  to  throw 
off  the  carbon  residue  which  has  remained  on  the  work,  and  in 
its  place  on  the  iron  there  is  deposited  a  thin  film  of  copper 
which  the  zinc  readily  covers.  When  the  copper  begins  to  show  red, 
then  you  know  the  work  is  clean. 

Small  material,  such  as  bolts,  nuts,  washers,  rivets,  etc.,  is 
handled  in  practically  the  same  manner,  except  that  no  scrubbing 
of  the  material  is  required  after  leaving  the  pickling  bath,  the 
same  results  being  accomplished  by  tumbling  it  in  revolving 
barrels. 

Castings,  according  to  size,  are  handled  in  a  like  manner,  ex- 
cept that  cold  hydrofluoric  acid  is  used  for  pickling.  In  some 
instances  slight  heating  has  been  found  to  be  an  advantage,  and 
a  bath  of  hydrofluoric  acid  of  2  per  cent,  in  weight  answers  gen- 
eral requirements.  Sometimes  it  is  scarcely  possible  to  remove 
the  scale  from  steel  without  the  work  remaining  so  long  in  the 


PREPARING  WORK  FOR  ELECTRO -CJALVAXTZIXG        213 

pickle  that  the  softer  or  more  porous  parts  of  the  metal  will  he 
over-pickled. 

Tumbling  and  Sand  Blasting 

The  removing  of  oil,  grease,,  oxide  and  scale  from  small  articles 
in  quantities  is  done  by  the  means  of  tumbling  them  for  several 
hours  in  cast-iron  or  heavy  wooden  tumbling  barrels,  running  with 
a  speed  of  approximately  twenty  to  forty  revolutions  per  minute. 
The  articles  are  charged  into  the  drums  and  mixed  with  sawdust. 
The  sawdust  will  remove  and  absorb  the  grease,  and  the  rattling 
and  tumbling  of  all  the  articles  against  each  other  for  a  continuous 
length  of  time  will  remove  the  scale  and  oxide  and  produce  at  the 
same  time  a  smooth  and  bright  finish  to  the  articles.  It  is  a 
general  practice  to  fill  the  drum  about  one-third  with  small  articles 
and  one-third  with  sawdust,  and  this  sawdust  is  discharged  at  the 
completion  of  the  process  by  simply  loosening  the  cover  of  the 
drum  a  little  and  the  sawdust  will  escape  through  the  opening 
in  the  revolution  of  the  drum.  After  the  sawdust  is  removed 
entirely,  a  few  shovels  of  new-  and  clean  sawdust  are  placed  into 
the  drum  again,  and  the  process  repeated  to  remove  the  balance 
of  the  grease,  if  any. 

Castings  are  freed  from  scale  and  sand  preferably  by  the  use 
of  a  horizontal  sand-blast  tumbling  barrel.  It  is  considered  good 
practice  to  wet  roll  stamped  steel  with  grit  or  emery  until  clean. 
Wire  work  can  usually  be  cleaned  l.y  dry  rolling  with  sawdust  to 
absorb  the  oil,  then  rolling  with  leather  chips  until  bright  and 
clean.  The  work  is  then  strung  on  wires  or  racks  and  hung  in 
the  electro-cleaner  for  a  short  time. 

The  use  of  sand  blast  is  recommended  where  the  nature  of  the 
material  and  quantity  make  the  operation  practicable.  Its  use  elim- 
inates the  necessitv  of  the  regular  pickling  process,  although  some- 
times moderate  subsequent  treatment  is  necessary  before  the  mate- 
rial is  placed  in  the  galvanizing  solution.  This  process  is  also 
extensively  used  for  cleaning  conduit  pipe  previous  to  electro- 
galvanizing. 

Oils  and  greases  should  be  removed  previous  to  being  sand 
blasted,  to  permit  the  sand  or  crushed  steel  employed  to  be  used 
again. 

Schulte  Grinding  and  Scouring  Machine 

The  object  of  the  machine  illustrated  in  detail  in  Fig.  08 
is  to  provide  a  new  and  improved  machine  for  grinding. 


214 


GALVANIZING  AND  TINNING 


scouring,  scratch-brushing,  buffing,  and  sand-buffing  sheet  metal, 
band-iron,  wire,  and  like  metal  articles  and  arranged  to  simul- 
taneously treat  both  faces  of  the  article  in  a  comparatively  short 
time  without  requiring  skilled  labor. 


FIG.  98.   FRONT  SIDE  ELEVATION  OF  SCHULTE  (^RINDING  AND  SCOURING 
MACHINE 

Suitable  grinding  material — such  as  water,  sand,  pumice-stone, 
and  the  like — is  fed  onto  the  top  and  bottom  of  the  article  to  be 
treated  immediately  previous  to  the  article  passing  between  the 
rollers  B  and  B1,  and  for  this  purpose  a  number  of  nozzles  N"  and  0 
are  employed,  connected  with  the  lower  end  of  a  tank  N1,  sup- 
ported on  the  top  of  the  frame  A  and  containing  the  grinding 
material  referred  to.  Now  as  the  article  moves  forward  between 
the  rollers  B  and  B1  the  grinding  material  discharged  onto  both 
faces  of  the  article  is  carried  along  by  the  latter,  and  consequently 
the  rotating  and  transversely  shifting  rollers  B  and  B1  grind,  rub, 
and  scour  both  surfaces  of  the  article.  In  order  to  keep  the  mate- 
rial in  the  tank  N1  properly  mixed,  a  stir-up  and  transversely  ex- 
tending screw  N"2  is  arranged  in  the  bottom  of  the  said  tank,  and 
on  the  outer  end  of  the  shaft  N3  of  the  said  screw  is  secured  a 
pulley  1ST4,  connected  by  a  belt  Nr>  with  a  pulley  Nc,  secured  to 
the  shaft  I)3  for  the  upper  feed  roller  D,  so  that  when  the  latter 
is  rotated  the  screw  N"2  in  the  tank  N1  is  rotated  to  agitate~anid 
keep  the  ingredients  of  the  grinding  material  properly  mixed.  It 
is  understood  that  instead  of  the  screw  N2  other  suitable  means 
may  be  employed. 

Water  is  discharged  on  the  upper  and  lower  faces  of  the  article 
to  be  treated  previous  to  the  article  passing  between  the  second 
pair  of  rollers  C  and  C1,  and  for  this  purpose  nozzles  O2  and  O3 


PREPARING  WORK  FOR   ELECTRO-GALVANIZING  21 5 

a:o  provided,  connected  with  a  water-supply  pipe  O4,  leading  from 
a  suitable  source  of  water  supply.  Xow  by  the  article  passing 
between  the  rollers  C  and  C1  while  the  latter  are  rotated  and 
shifted  bodily  and  water  is  discharged  onto  the  plate  at  both  faces, 
it  is  evident  that  the  article  receives  a  final  scrubbing,  so  that 
the  article  finally  passes  in  a  ground  and  scoured  condition  to  the 
delivery-rollers  E  and  E1  and  the  transporting-rollers  F1  for  carry- 
ing the  finished  article  off  the  machine. 

The  grinding  material  used,  as  well  as  the  water,  drips  and 
flows  into  a  trough  P,  arranged  in  the  lower  portion  of  the  main 
frame  A  below  the  rollers  B1  and  C1,  and  this  trough  P  is  con- 
nected with  the  suction  end  of  a  pump  Q,  having  its  discharge- 
pipe  Q1  leading  into  the  overhead  tank  N1,  so  that  the  grinding 
material  and  water  is  returned  to  the  said  tank  N1  to  be  again 
discharged  to  the  nozzles  N"  onto  both  faces  of  the  next  article 
to  be  treated,  thus  allowing  reuse  of  the  grinding  material.  The 
shaft  Q2  of  the  pump  Q  is  provided  with  a  pulley  Q3,  connected 
by  a  belt  Q4  with  a  pulley  Q3  on  the  shaft  B3  of  the  roller  B1, 
so  that  when  the  latter  is  rotated  the  rotary  pump  Q  is  set  in 
motion  to  pump  the  material  from  the  trough  P  into  the  over- 
head tank  N1. 

It  is  understood  that  when  the  machine  is  in  operation  both 
faces  of  the  article  are  ground  and  scoured  by  the  use  of  the 
grinding  material  discharged  onto  both  faces  of  the  article  previous 
to  its  passage  between  the  rollers  B  and  B'. 

The  pairs  of  rollers  B  B'  and  C  C'  are  made  of  wood  or  other 
suitable  material  or  covered  with  a  fabric.,  according  to  the  nature 
of  the  material  under  treatment  and  according  to  the  particular 
finish  to  be  given  to  the  article — that  is,  whether  the  same  is  to 
receive  a  scratch-brushing,  buffing,  sand-buffing,  or  the  like.  By 
passing  the  article  in  an  inclined  position  through  the  pairs  of 
rollers  the  grinding  material  and  water  readily  flow  back  on  the 
article  and  finally  into  the  trough. 

Electro  Cleaning 

Cleaning  work  by  a  low  current  of  electricity  is  largely  prac- 
ticed in  the  electro-plating  industry.  Usually  an  alkaline  solu- 
tion is  used,  costing  but  a  few  cents  per  gallon.  Steel  or  iron  con- 
tainers are  used  for  the  bath,  which  is  heated  to  the  boiling  point 
by  means  of  steam  coils.  The  tank  itself  is  made  the  positive  by 


216  GALVANIZING  AND  TINNING 

being  connected  with  the  positive  pole  of  the  generator;  the  work 
in  the  bath  is  attached  to  the  negative  pole  of  the  dynamo  and  an 
e.  m.  f.  of  6-8  volts  is  used,  the  work  being  left  under  the 
influence  of  the  current  for  several  minutes.  Gas  is  thrown  off 
freely  from  the  work  and  the  surface  is  cleaned  by  the  action  of 
this  gas,  particles  of  oxide  and  grease  being  removed. 


CHAPTER  XXIII 

Electro-Galvanizing  Solutions  and  Their  Application 

SOME  of  the  earliest  experiments  in  electro  galvanizing  were 
made  by  the  French  scientists,  and  present  users  are  indebted 
to  this  source,  as  well  as  to  German  and  English  authorities, 
for  some  practical  information  regarding  the  action  of  the  various 
salts  of  zinc.  A  number  of  baths  have  been  patented  both  in  this 
country  and  abroad,  but  the  most  effective  and  simplest  bath  is 
that  made  from  the  sulphate  of  zinc,  in  combination  with  alu- 
minum, zinc  chloride  or  some  similar  salt,  and  it  has  been  deter- 
mined that  a  bath  showing  an  acid  reaction  is  to  be  preferred. 

It  is  unnecessary  that  solutions  be  used  of  a  composition  of 
poisonous  ingredients  or  those  throwing  off  fumes  while  in  opera- 
tion, nor  is  it  necessary  to  operate  them  at  more  than  the  usual 
room  temperature.  Their  composition  should  be  such  as  to  give 
the  highest  electrical  conductivity;  for  the  thickness  of  the  zinc 
deposit  and  the  length  of  time  required  for  the  coating  depends 
on  the  conductivity  to  a  large  extent.  Their  nature  should  be 
such  as  to  decompose  and  deposit  the  zinc  with  a  minimum  libera- 
tion of  hydrogen,  or  the  deposit  is  likely  to  be  found,  on  exam- 
ination, to  be  porous  and  of  a  granular  and  spongy  nature.  Ob- 
servance of  these  conditions  will  result  in  deposits  uniformly 
smooth,  homogeneous,  flexible  with  perfect  adhesion,  and  in  an 
absolute  union  between  the  basic  metal  and  coating. 

The  upkeep  or  maintenance  of  the  solution  is  equally  impor- 
tant, and  satisfactory  results  cannot  be  obtained  continuously  un- 
less the  solutions  are  at  all  times,  working  at  their  highest  efficiency. 

The  cause  of  unsatisfactory  work  with  the  electro-galvanizing 
process  is  frequently  attributed  to  improper  cleaning  of  the  mate- 
rial, but  the  fault  sometimes  lies  with  the  electro-galvanizing  solu- 
tion or  electrolyte.  While  experience  in  pickling  or  preparation  of 
surfaces  previous  to  galvanizing  affords  many  little  short-cuts  which 
will  result  in  the  most  satisfactory  and  quickest  results,  it  does 
not  require  the  services  of  an  expert  or  a  man  of  more  than  average 
intelligence  to  master  it  in  a  comparatively  short  time.  Atten- 
tion to  details  and  close  observance  of  results  under  varying  con- 

217 


218  GALVANIZING  AND  TINNING 

ditions  will  enable  any  one  to  master  this  part  of  the  electro- 
galvanizing  process. 

The  electrolyte  or  zinc  solution  can  be  made  up  from  sulphate 
of  zinc  (white  vitriol)  or  from  chloride  of  zinc,  or  from  a  com- 
bination of  the  two.  An  addition  of  conducting  salts,  such  as 
sulphate  of  sodium,  sulphate  of  aluminum,  chloride  of  ammonia, 
etc.,  can  be  used  to  increase  the  conductivity  of  zinc  solutions. 
There  are  also  a  number  of  organic  and  inorganic  chemicals  rec- 
ommended and  patented  for  the  purpose  of  producing  a  more 
dense  and  brighter  deposit.  The  majority  of  these  chemicals  (of 
which  we  will  speak  more  fully  later  on)  act  as  a  colloid  through 
the  electric  current.  The  following  solution  has  been  worked  with 
success  in  an  open  still  tank. 

Formula  1 

Zinc  sulphate 200  Ibs. 

Sulphate  of  sodium  (crystals ) 20  Ibs. 

Sulphate  of  aluminum 10  Ibs. 

Boric  acid 3  Ibs. 

Water  to  make  100  gallons. 

An  addition  of  a  few  pounds  of  zinc  chloride,  or  instead  a  pint 
of  hydrochloric  acid,  will  improve  the  solution  to  some  extent; 
also  an  addition  of  grape  sugar  will  improve  a  sulphate  of  zinc 
solution  and  produce  a  smoother  and  more  uniform  finish,  at 
the  same  time  preventing  the  formation  of  spongy  deposits. 

The  above  solution  can  be  successfully  used  for  all  kinds  of 
articles,  including  wire,  band  iron,  sheets  and  wire  cloth,  and  will 
produce  by  three  volts  and  about  twenty  amperes  per  square  foot 
a  white,  smooth  deposit  in  thirty  minutes  which  will  stand  three 
one-minute  copper  tests,  of  which  we  will  speak  later  on. 

Chloride  of  zinc  solutions  can  also  be  used  to  better  advantage 
in  open  tank  work,  as  well  as  in  mechanical  plating  machines.  A 
good  solution  is  composed  of  the  following: 

Formula  2 

Zinc  chloride 100  to  150  Ibs. 

Chloride  of  ammonia 50  to     75  Ibs. 

Grape  sugar 10  Ibs. 

Water  to  make  100  gallons. 


ELECTRO-GALVANIZING  SOLUTIONS  219 

In  the  open  bath  a  low  e.  m.  f.  is  used,  ahout  3  volts  being 
required  with  a  current  of  12  to  15  amperes  per  square  foot  of 
work  surface,  the  density  of  the  solution  being  about  20  deg. 
Baume,  although  a  higher  voltage  can  be  used  if  it  is  desired  to 
shorten  the  time  of  deposit.  For  mechanical  apparatus,  where  the 
revolving  container  is  used,  the  solution  is  brought  to  a  density 
of  25  to  30  deg.  Baume  and  8  to  10  volts  are  used  with  a  corre- 
sponding increase  in  current. 

The  following  zinc  solutions  have  also  been  used  satisfactorily  on 
different  classes  of  work  and  under  varying  condition.  They  are 
given  here  so  the  user  of  the  book  may  have  a  basis  on  which  to 
work  in  experimenting  to  find  the  solutions  best  suited  to  his 
apparatus  and  work: 

Formula  3 

Zinc  sulphate '. .  -4-4       Ihs. 

Pure  crystallized  sodium  sulphate 8.8  Ibs. 

Chemically  pure  zinc  chloride 2.2  Ibs. 

Crystallized  boric  acid 1.1  H>s. 

Water    25       gals. 

Worn/into.  -4 

Zinc  sulphate 50       Ibs. 

Ammonium  chloride 3.1  Ibs. 

Aluminum  sulphate 0.2  Ibs. 

Water    25       gals. 

Foftn  ul 1 1  5 
Cold  galvanizing  solution  for  eastings: 

Zinc   sulphate H  Ibs. 

Ammonium  chloride 3  oz. 

Sulphuric  acid 4  oz. 

Water 1  gal. 

Formula  6 
Cold  galvanizing  solution  for  barrel  plating: 

Zinc  sulphate 2|  Ibs. 

Ammonium  chloride 6     oz. 

Sulphuric  acid -4     oz. 

Water 1     gal. 


220  GALVANIZING  AND  TINNING 

Formula  7 
Another  for  regular  work: 

Zinc  sulphate 1£  Ibs. 

Epsom  salts 8  oz. 

Boric  acid 4  oz. 

Ammonium  chloride 4  oz. 

Water 1  gal. 

Formula  8 

This  solution  will  give  a  soft  deposit  that  will  stand  bending 
and  forming: 

Zinc  sulphate 2     Ibs. 

Ammonium  chloride 2     oz. 

Sulphuric  acid ^  oz. 

Water 1     gal. 

Formula  9 

Sulphate  of  zinc 1 J         Ibs. 

Epsom  salts 5  oz. 

Sulphuric  acid 1/10  oz. 

Water 1  gal. 

Formula  10 

Zinc  sulphate 2  Ibs. 

Sodium  sulphate 4  oz. 

Zinc  chloride 2  oz. 

Boric  acid 1  oz. 

Water 1  gal. 

Dextrine 4  oz. 

Formula  11 

Zinc  sulphate 1  Ib. 

Ammonium  chloride 4  oz. 

Sodium  sulphate 3  oz. 

Sulphuric  acid 2  oz. 

Water 1  gal. 

Formula  12 

Zinc  sulphate 2     Ibs. 

Aluminum  sulphate   2     oz. 

Glycerine     |  oz. 

Dextrine    2     oz. 

Water 1     gal, 


ELECTRO-GALVANIZING  SOLUTIONS  221 

Formula  13 

Zinc  sulphate   2  Ibs. 

Sulphuric  acid 1  oz. 

Gum  tragacanth 1  oz. 

Water 1  gal. 

Formula  14 

Sodium  citrate    (crystals) 5.5  Ibs. 

Zinc  chloride 8.8  ll>s. 

Ammonium  chloride 6.0  Ibs. 

Water    25       gals. 

Formula  15 

Zinc  chloride 2  Ibs. 

Sal  ammoniac 10  oz. 

Common  salt 3  oz. 

Tartaric  acid 3  oz. 

Water : 1  gal. 

Formula  16 

Zinc  chloride 1  Ib. 

Sodium  aluminum  chloride 5  oz. 

Common  salt 4  oz. 

Grape  sugar    5  oz. 

Formula  17 

Zinc  sulphate 2     Ibs. 

Iron  sulphate 2     oz. 

Aluminum  sulphate ^  oz. 

Sodium  acetate ^  oz. 

Formula  18 

Zinc  sulphate H  Ibs. 

Sal  ammoniac  1     oz. 

Sulphate  of  soda 2     oz. 

Sulphuric  acid 1     oz. 

Water 1     gal. 

Formula  1!) 

Zinc  chloride 2  Ibs. 

Sal  ammoniac  10  oz. 

Tartaric  acid    3  oz. 

Sodium  chloride 3  oz. 

Water , . . , , 1  gal, 


222  GALVANIZING  AND  TINNING 

Formula  20 

Sulphate  of  zinc 2  Ibs. 

Sulphate  of  aluminum 4  oz. 

Sal  ammoniac 2  oz. 

Sodium  sulphate 3  oz. 

Water 1  gal. 

Agents  for  Improving  Solutions 

The  following  additional  agents  are  used  to  improve  either  the 
sulphate  or  chloride  solutions,  and  will  cause  them  to  plate  brighter 
and  prevent  the  formation  of  large  crystals.  A  majority  of  these 
additional  agents  are  embodied  in  numerous  patented  formulas: 

Gelatine,  dextrine,  glue,  alum,  powdered  licorice,  gum  traga- 
canth  and  tannic  acid.  These  are  called  "colloids,"  and  when 
used  as  additional  agents  form  colloidal  solutions  or  suspensions. 
They  cause  the  solutions  to  deposit  a  smaller  crystal,  making  a 
close-grained,  smooth,  bright  coating. 

Glucose,  molasses,  benzoic  acid,  alcohol,  sugar  and  pyrogallol 
are  strong  reducing  agents,  and  when  used  in  from  three  to  five 
per  cent,  additions  produce  a  smooth  deposit  with  great  adherence. 

Applying  the  Coating 

After  the  articles  have  been  freed  of  all  oxides  and  scales,  which 
means  the  completion  of  the  pickling  process,  the  goods  are  then 
suspended  on  wires,  hooks  or  racks  and  thoroughly  rinsed  in  run- 
ning water  and  after  this  operation  without  any  delay  are  sus- 
pended in  the  zinc  electrolyte  from  a  rod  between  two  zinc  anodes. 
The  anodes  also  being  suspended  on  rods  opposite  to  the  work- 
ing rod.  The  working  rod  is  connected  with  the  negative  pole 
of  the  dynamo  and  the  two  anode  rods  are  connected  to  the  posi- 
tive pole  of  the  dynamo,  marked  with  "-J-"  sign. 

If  the  tumbling  of  the  smaller  goods  has  been  accomplished  sat- 
isfactorily, there  is  no  further  operation  necessary  and  the  articles 
can  be  transferred  from  the  tumbling  machinery  directly  into  the 
mechanical  plating  device,  in  which  they  remain  from  thirty  min- 
utes to  one  and  one-half  hours,  according  to  the  quantity  of  goods 
to  be  plated  at  one  time,  also  according  to  the  different  types  of 
machine  in  use,  but  chiefly  according  to  thickness  of  coating 
required. 

There  are  quite  a  number  of  plating  machines  on  the  market 


ELECTRO-GALVANIZING  SOLUTIONS  223 

to-day  particularly  adapted  for  the  plating  of  small  articles  in 
large  quantities,  by  the  means  of  revolving  barrels,  having  nega- 
tive connections;  connecting  with  the  goods  to  be  plated  and  mix- 
ing same  thoroughly  within  the  barrel,  and  thus  each  and  every 
article  receives  an  equal,  uniform  plating.  These  mechanical 
platers  differ  from  each  other  more  or  less  in  their  construction, 
also  in  the  arrangement  of  their  anodes;  some  are  used  outside 
of  the  barrel  and  some  within  the  drum  only.  These  have  been 
fully  described  and  their  operation  explained  in  Chapter  XXI. 

Work  with  deep  depressions  cannot  be  coated  satisfactorily  with- 
out using  anodes  shaped  to  fit  the  depressions.  Increasing  the 
voltage  to  make  it  throw  in  would  not  make  it  cover,  but  would 
result  in  the  outer  points  becoming  granular  or  burnt. 

Spongy  deposits  arc  caused  by  a  too  neutral  condition  of  the 
bath,  and  this  can  be  rectified  by  testing  the  solution  with  blue 
litmus  paper.  This  test  should  show  a  deep  red  at  once  if  the 
solution  is  in  proper  condition,  but  there  should  not  be  enough 
free  acid  to  blue  Congo  paper. 

If  the  bath  becomes  neutral,  a  ten-per-cent.  solution  of  sulphuric 
acid  and  water  should  be  added  until  blue  litmus  paper  shows  a 
proper  reaction. 

Such  articles  as  castings,  fittings,  stampings,  etc.,  that  have 
recesses  and  depressions,  should  have  some  previous  treatment. 

The  method  of  procedure  is  that  the  fixed  time  of  electro-gal- 
vanizing be  cut  in  two.  A  strike  or  preliminary  zinc  coating 
is  deposited  from  a  specially  prepared  zinc  solution  and  is  of  a 
dull  gray  or  matt  finish.  It  is.  advisable  then  to  finish  the  mate- 
rial in  the  regular  or  finish  solution,  which  will  then  readily  coat 
over  the  entire  surface  and  leave  the  treated  material  of  a  bright 
silvery  appearance.  Its  value  can  be  appreciated  from  the  fact 
that  it  is  productive  of  a  quality  of  work  not  possible  by  any 
other  means,  reduces  the  time  of  coating  and  results  in  an  out- 
put of  more  than  double  that  possible  with  the  same  size  equip- 
ment containing  only  the  ordinary  electro-galvanizing  solution  or 
electrolyte.  A  zinc  coating  of  25  to  35  minutes,  depending  on 
the  nature  of  the  material,  deposited  in  this  manner  is  ample  and 
will  be  found  to  answer  all  requirements. 

It  is  possible  to  make  a  heavier  deposit  by  electro-galvanizing 
processes  by  leaving  in  the  solution  for  a  long  period.  Cast-iron 
rolls  have  been  electro  galvanized  with  coating  heavy  enough  to 


224  GALVANIZING  AND  TINNING 

stand  turning  in  lathe.     This  required  about  ten  hours  in  the 
regular  solutions. 

Cost  of  Operation 

The  cost  of  labor  and  power  are  the  main  items  of  expense  in 
electro  galvanizing.  Exact  figures  as  to  the  cost  of  power  cannot 
be  given.  A  larger  firm  producing  their  own  steam  and  electric 
power  as  a  by-product,  figure  the  cost  per  kilowatt  hour  as  less 
than  one  cent;  while  a  small  consumer  supplied  with  electricity 
by  a  local  power  and  light  company  has  to  pay  from  four  to  eleven 
cents  per  kilowatt  hour,  while  in  comparison  the  cost  of  fuel 
for  a  hot  galvanizing  process  does  not  differ  to  such  an  extent. 
The  labor  cost  in  electro  galvanizing  and  in  hot  galvanizing  is 
about  the  same,  while  the  zinc  wasted  in  the  hot  process  in  the 
form  of  dross  seems  to  be  greater  than  the  zinc  wasted  by  the  cold 
process  in  rinsing  the  work  from  the  solution.  After  a  length 
of  time,  however,  if  the  possible  leakage  of  tanks  and  the  renewing 
of  the  solution  is  taken  into  consideration,  the  cost  of  waste  in 
comparing  the  two  processes  will  average  about  the  same. 

While  more  time  and  chemicals  have  to  be  applied  for  the  electric 
process  than  for  a  hot  process,  the  hot  process  will  use  a  larger 
amount  of  zinc  metal  by  one  dip,  and  this  leads  to  the  main  argu- 
ment as  to  whether  cold  galvanizing  is  cheaper  and  better  or 
whether  the  hot  galvanized  articles  are  superior  and  cheaper  than 
the  others. 

While  the  unskilled  workman  in  a  hot  galvanizing  plant  cannot 
prevent  the  giving  of  the  iron  articles  to  be  coated  a  sufficiently 
heavy  zinc  coating,  the  skilled  workman  in  an  electro-galvanizing 
plant  is  sometimes  forced,  through  local  conditions,  to  give  the  cus- 
tomer an  inferior  galvanized  article.  Therefore,  aside  from  the 
above  facts,  it  can  be  easily  determined  in  any  galvanizing  plant 
using  the  two  processes  that,  if  an  equal  amount  of  metal  is 
required  on  sheets,  for  example,  by  the  hot  process,  as  well  as 
by  the  cold  process,  the  cost  of  operating  and  materials  for  the 
cold  process  will  exceed  that  of  the  hot  process.  However,  small 
work  in  bulk  quantities  plated  in  up-to-date  mechanical  plating 
machines  is  less  expensive  than  the  hot  process. 

Numerous  arguments  have  arisen  to  set  forth  that  a  dense  and 
bright  coherent  electro-galvanized  deposit  does  not  require  so  much 
zinc  deposit  as  a  zinc  coating  produced  by  the  hot  process.  This 
problem  is  still  open  for  discussion,  but  practical  natural  tests 


ff.  Imhoff 

ELECTRO-GALVANIZING  SOLUTIONS  225 

for  a  number  of  years,  under  the  same  conditions,  have  proved  that 
the  amount  of  zinc  applied  to  iron  will  guarantee  the  length  of 
time  the  iron  is  protected  from  corrosion. 

For  example,  large  pieces  of  iron  sheets  galvanized  by  the  hot 
process  and  -large  pieces  of  iron  sheets  galvanized  by  the  cold 
process  were  nailed  on  top  of  a  roof  and  additional  pieces  nailed 
against  the  chimney  of  a  factory,  and  in  each  instance,  where  there 
was  less  zinc  on  the  cold  galvanized  sheets,  the  galvanizing  broke 
down  before  the  hot  galvanized  sheets.  This  refers  especially  to 
such  articles  where  the  electro  galvanizing  does  not  enter  so  easily 
into  the  deeper  parts  of  profiled  articles,  and  consequently  the  dif- 
ference between  hot  and  cold  galvanizing  will  be  much  earlier 
shown. 

That  this  point  has  been  thoroughly  recognized  and  practiced 
is  evidenced  by  the  process  of  plating  employed  at  the  electro- 
galvanizing  plant  of  the  Spirella  Company,  Niagara  Falls,  N.  Y., 
illustrations  of  which  are  given  in  Figs.  56  and  57.  The  problem  of 
supplying  corset  wires  which  would  effectively  resist  corrosive  at- 
tack, due  to  atmospheric  moisture  and  perspiration,  was  a  serious 
one.  Numerous  experiments  for  several  years  resulted  in  the 
following  coatings  being  applied.  The  wires  are  placed  for  45 
minutes  in  a  copper  cyanide  bath,  45  minutes  in  an  acid  copper  solu- 
tion, 20  minutes  in  a  nickel  solution  and  90  minutes  in  a  gal- 
vanizing solution.  This  is  an  exceptional  case  and  is  interesting 
as  probably  representing  the  limit  of  practice  in  plating  for  pro- 
tection, about  five  pounds  of  metal  being  deposited  for  every  one 
hundred  pounds  of  corset  wire. 

The  argument  about  the  special  test  is  also  a  delicate  one.  The 
Preece  test  adopted  by  the  United  States  Government  is  the  most 
reliable  and  quickest  of  all  tests,  and  every  electro-galvanizing  plant 
should  use  it,  if  only  for  the  purpose  of  determining  or  controling 
the  deposition  of  zinc  from  the  different  solutions  every  day. 

The  saline  or  salt-water  test,  by  the  means  of  spraying  contin- 
uously a  10-per-cent.  salt  solution  for  a  period  of  from  14  to  20 
days  all  over  the  galvanized  articles,  is  also  adopted  by  some  con- 
cerns. Galvanizing  which  breaks  down  before  14  days  have  elapsed 
is  rejected  as  inferior. 

Another  test  is  to  hang  the  galvanized  articles  in  a  pure-water 
bath  in  which  a  continuous  stream  of  air  is  flowing. 

There  is  also  the  cinder  test  and  sometimes  diluted  sulphuric 
acid  is  used  to  test  galvanized  articles  against  quick  corrosion. 


226  GALVANIZING  AND  TINNING 

Test  for  Thickness  of  Zinc  Coating  on  Armored  Cable  Strip 

as  Provided  by  Underwriters'  Laboratories,  in  Effect 

September  i,  1913 

The  following  test  is,  in  some  degree,  a  measure  of  the  thickness 
of  the  zinc  coating  and  should  be  made  on  at  least  two  samples 
(about  4  in.  long)  of  the  finished  product  going  through  at  the 
time  of  each  visit.  Each  sample  shall  be  washed  in  running  water 
and  then  dipped  up  and  down  in  a  vessel  containing  either  carbon 
tetrachloride  or  ether  and  allowed  to  dry  before  being  put  into 
the  copper  sulphate  solution.  This  solution  is  a  saturated  solu- 
tion of  C.  P.  sulphate  of  copper,  using  distilled  water. 

About  100  cubic  centimeters  of  the  solution  shall  be  poured 
into  a  glass  vessel  about  two  inches  in  diameter.  The  same  sample 
of  solution  shall  be  used  for  all  dips  of  any  one  sample,  but  a 
new  supply  of  solution  shall  be  used  for  each  new  sample.  Solu- 
tion, after  use,  shall  be  thrown  away  and  in  no  case  put  back  into 
the  supply  bottle.  The  portion  of  solution  used  for  each  test  shall 
be  brought  to  a  temperature  of  approximately  65  deg.  Fahrenheit 
before  the  test  is  made.  This  shall  be  accomplished  by  setting  the 
beaker  containing  the  solution  in  a  larger  vessel  containing  the 
warmer  or  colder  water  and  stirring  the  solution  with  a  glass 
thermometer  until  the  proper  temperature  is  obtained. 

The  sample  prepared,  as  above,  shall  be  stood  on  end  in  the 
solution  for  one  minute.  The  solution  shall  not  be  stirred  or 
the  sample  moved  during  the  immersion.  At  the  end  of  one 
minute  the  sample  is  to  be  removed  from  the  solution  and  rinsed 
in  running  water  and  then  wiped  lightly,  both  inside  and  out, 
with  cheesecloth  until  dry.  Care  should  be  taken  to  avoid  violent 
rubbing  of  the  sample  and  the  contact  of  the  surface  with  the  hand 
or  anything  else  than  the  white  cloth  used  for  drying.  The  sample 
must  be  thoroughly  dried  before  each  dip. 

Each  sample  shall  be  subjected  to  at  least  three  dips  and  the 
dips  should  generally  be  continued  until  the  entire  immersed  sur- 
face of  the  sample  is  coated  with  a  fixed  copper  deposit. 

The  coating  will  be  considered  satisfactory,  so  far  as  this  test 
is  concerned,  if  the  fixed  copper  deposit  (i.e.,  that  which  cannot 
be  wiped  off)  does  not  show  before  the  second  dip  and  also  does 
not  appear  on  more  than  25  per  cent,  of  the  surface  tested  before 
the  third  dip  and  wiping  process. 


CHAPTER  XXIV 

The  Art  of  Sherardizing 

SHERAEDIZING,  or  dry  galvanizing,  is  a  process  whereby 
articles  of  iron  and  steel  are  rendered  rust  proof  by  applying 
a  coating  of  zinc  dust.    The  coating  produced  by  this  process 
is  first  an  alloy  with  the  'underlying  metal.     After  this  alloying 
action  is  completed  the  outer  layer  of  zinc  is  deposited,  the  zinc 
penetrating  into  every  crevice  and  cavity  radically  different  from 
any  other  method  of  zinc  coating.     Briefly  stated,  this  coating  is 
not  a  pure  layer  of  zinc,  but  a  zinc-iron  alloy. 

Dry  Galvanizing  in  Prehistoric  Times 

A  process  practically  identical  to  this  was  known  in  prehistoric 
times,  although  used  for  another  purpose.  At  that  time  it  was 
known  that  if  certain  copper  tools  and  vessels  were  placed  in  the 
ground  in  certain  localities  and  kept  hot  for  a  time  by  building 
fires  over  the  place,  then,  on  removal,  it  was  seen  that  the  copper 
had  assumed  a  light  yellow  color  and  had  become  harder  and  more 
durable.  They  practically  secured  dry  galvanizing,  although  it  was 
not  known  that  another  metal  was  being  alloyed  with  the  copper. 
Also,  in  Greek  History,  according  to  Aristotle,  the  "bleaching  of 
copper"  was  done  by  the  same  method. 

The  Sherardizing  process  was  discovered  by  accident.  Com- 
mander H.  V.  Simpson,  of  the  English  navy,  was  detailed  to  work 
out  a  method  of  case  hardening  armor  plate  for  battleships  that 
would  not  infringe  on  the  Harvey  patents  which  were  being  used 
by  nearly  all  governments  for  rendering  armor  plate  shell  proof. 
These  experiments  were  being  tried  out  in  the  laboratory  of  Sherard 
Cowper-Cowles,  of  London,  a  noted  English  metallurgist.  A  pack- 
age of  zinc  dust  had  been  forwarded  Mr.  Cowper-Cowles  to  de- 
termine whether  it  could  be  used  in  making  an  electrolyte  for  zinc 
plating.  In  the  course  of  their  experiments  they  placed  a  piece 
of  steel  in  this  zinc  dust  in  a  case  hardening  oven  and  heated  it  up 
to  see  if  it  would  have  any  hardening  effect  on  metal.  When  taken 
out  it  was  covered  with  a  silvery  coating  of  zinc  and  on  examining 

227 


228  GALVANIZING  AND  TINNING 

under  the  microscope  they  found  it  had  penetrated  and  alloyed 
the  zinc  with  the  body  of  the  metal. 

Theory  of  Sherardizing 

Sherardizing  may  be  defined  as  a  process  of  sublimation,  occlu- 
sion and  adhesion,  when  considered  in  connection  with  the  theory 


FIG.  99.    SECTION  OF  SHERARDIZED  STEEL  MAGNIFIED  100  TIMES 

of  ions.  The  process  of  passing  directly  from  the  solid  to  the 
gaseous  state  and  from  the  gaseous  direct  to  the  solid  state,  in 
both  cases  stepping  over  the  liquid  state,  is  called  sublimation. 

The  theory  of  sublimation  and  the  ''triple  point"  in  connection 
with  sublimation  is  fully  defined  and  described  in  many  elements 
of  physics.  It  is  a  very  well  known  fact  that  solids  sublime.  This 
is  easily  shown,  for  example,  in  the  evaporation  of  ice  when  it  is 
kept  below  its  melting  point.  In  the  case  of  most  solid  substances 
this  process  is  so  slow  at  ordinary  temperature  that  it  cannot  be 
detected.  At  ordinary  temperature  and  pressure  camphor,  arsenic 
and  many  less  familiar  substances  sublime.  Solid  carbon  dioxide 
will  volatilize  at — 79  deg.  C.  at  atmospheric  pressure  without 
passing  through  the  liquid  state.  Zinc  as  a  solid  may  change  into 
vapor  without  passing  into  the  liquid  state.  For  an  exact  definition 
of  the  physical  condition  of  a  body  a  knowledge  of  the  values  of  all 
its  variable  properties  is  required.  The  three  most  important  of 
these  are  temperature,  pressure  and  volume  occupied  by  unit  mass 
of  the  substance.  These  are  not  independent  of  each  other  but  are 
connected  by  a  definite  relation  called  the  equation  of  state,  which, 


THE  ART  OF  SIIERARDI/IXC;  220 

in  the  simple  state  of  perfect  gases,  takes  the  form  of  the  gas  law, 
which  is  the  law  of  Boyle  and  Charles. 

It  is  a  well  known  fact  that  common  metals  are  extremely  porous. 
This  is  visible  under  a  high  power  magnifying  glass,  as  well  as 
readily  demonstrated  by  certain  physical  experiments.  Thus,  if  an 
iron  wire  be  placed  in  a  vacuum  tube  and  then  heated  to  incan- 


FIG.  100.    SECTION  OF  COI.D  ROLLED  SHERARDIZED  STEEL  MAG- 
NIFIED  1300  TIMES.    NOTE  /INC- IRON   ALLOY 

descence,  as,  for  instance,  by  passing  a  current  through  the  wire, 
the  pressure  within  the  tube  rises  materially  and  gas  is  evolved  for 
a  very  considerable  time,  indicating  that  iron  (and  practically  all 
other  metals)  contain  large  volumes  of  gases.  The  condition  of 
the  metal  may  be  graphically  described  as  resembling  a  sponge 
soaked  with  water. 

The  two  photomicrographs  reproduced  in  Figs.  99  and  100  show 
pieces  of  Sherardized  steel  magnified  so  as  to  show  the  zinc  and 
iron  alloy  after  Sherardizing. 

How  Precipitation  of  a  Vapor  on  Metal  Occurs 

When  a  porous  solid  is  easily  permeated  by  a  gas  and  condensa- 
tion on  the  surface  of  the  pores  of  the  solid  takes  place,  it  is  called 
occlusion.  An  example  of  this  can  be  seen  in  the  absorption  of 
90  volumes  of  ammonia  in  one  volume  of  charcoal.  Spongy  plati- 
num will  absorb  about  250  times  its  own  volume  of  oxygen.  Pa- 
ladium  will  absorb  about  1000  times  its  own  volume  of  hydrogen 


230  GALVANIZING  AND  TINNING 

and  will  increase  one-tenth  of  its  volume.  To  produce  such  a 
condensation  alone  would  require  a  pressure  of  many  thousand 
pounds  per  square  inch.  Nearly  all  metals  absorb  gases  and,  being 
heated,  will  allow  them  to  pass  through  readily.  An  example  of 
this  is  the  fact  that  hydrogen  will  readily  pass  through  heated  iron. 

When  a  gas  is  in  contact  with  a  solid,  there  are  molecular  forces 
drawing  the  particles  together,  and  this  produces  a  surface  con- 
densation of  gas  on  the  solid.  An  example  of  this  is  the  difficulty 
in  removing  the  last  traces  of  air  from  a  vacuum  bulb  due  to  the 
adhesion  of  the  air  on  the  surface.  Another  example  is  the  frost- 
ing of  window  panes  in  irregular  figures. 

There  also  appears  to  be  an  electrical  condition  accompanying 
the  evolution  of  gases  from  a  metal  inasmuch  as  the  evolved  gases 
usually  contain  a  number  of  free  ions.  This  is  particularly  the 
case  if  the  temperature  of  the  metal  is  high  at  the  time  the  gases 
are  given  off.  Naturally  the  exposed  surface  of  the  metal  is  the 
only  portion  which  actively  takes  part  in  evolving  gases,  so  that 
the  larger  the  area  of  surface  exposed  the  greater  the  evolution  of 
gas,  other  conditions  being  equal. 

A  further  fact,  which  is  well  established,  is  that  the  presence 
of  free  ions  has  a  marked  effect  in  producing  a  precipitation  of  a 
vapor  or  suspended  matter  in  a  gas  It  follows,  therefore,  that 
if  a  metal  be  heated  in  the  presence  of  a  vapor  under  such  condi- 
tions that  the  gases  or  vapors  contained  within  the  metal  are  in 
part  liberated;  then,  as  the  liberated  gases  or  vapors  contain  some 
free  ions,  they  will  cause  the  precipitation  within  the  pores  of  the 
metal  and  on  the  surface  layer  of  a  portion  of  the  external  vapor 
in  which  the  metal  is  heated. 

Now  it  is  a  well  known  fact  that  all  materials  have  a  definite 
vapor  tension,  depending  mainly  on  the  nature  of  the  material,  the 
nature  of  the  surrounding  materials,  the  temperature  and  the 
pressure.  It  therefore  follows  that  under  all  conditions  all  sub- 
stances are  surrounded  by  a  certain  amount  of  their  own  vapor. 
The  vapor  can  be  increased  in  amount  by  increasing  the  tempera- 
ture and  decreasing  the  pressure. 

Methods  of  Producing  Zinc  Vapor 

Zinc  vapor  can  be  produced  in  several  ways  from  zinc.  If  molten 
zinc  is  boiled  in  a  reducing  atmosphere,  vapor  is  given  off  rapidly 
and  if  heated  iron  is  brought  in  contact  with  this  vapor  Sherardiz- 


THE  ART  OF  SHERARDIZING  231 

ing  would  take  place.  This  method,  however,  is  neither  convenient 
nor  economical  hecause  of  the  waste  of  zinc.  The  most  practical 
and  economical  method  is  to  use  zinc  dust,  which  is  obtained  as 
a  by-product  of  a  zinc  smelter.  This  dust  is  practically  amor- 
phous and  each  particle  consists  of  a  small  inner  particle  of  more 
or  less  pure  zinc  surrounded  by  a  thin  coating  of  zinc  oxide. 

According  to  a  well  known  fact,  the  vapor  tension  is  higher  for 
small  particles  than  for  large.  It  is  thus  desirable  that  the  zinc 
be  in  a  very  finely  divided  condition,  for  the  extent  or  degree  of 
penetration  of  the  zinc  vapor  in  the  iron  depends  upon  its  vapor 
tension.  It  is  also  desirable  that  there  be  as  little  impurity  in 
the  zinc  as  possible,  for  not  only  the  zinc,  but  also  the  impurities, 
such  as  lead,  cadmium,  etc.,  will  give  off  vapors,  and  the  combined 
vapor  tension  of  the  mixture  would  generally  be  less  than  that  for 
pure  zinc. 

As  said  before,  the  zinc  particles  are  surrounded  by  a  coating 
of  zinc  oxide.  This  oxide  is  very  inert  compared  to  metallic  zinc 
and  has  a  high  melting  point.  It  therefore  is  very  advantageous  in 
the  process  because  it  not  only  keeps  the  particles  of  zinc  separated, 
but  allows  the  spheres  of  vapor  surrounding  them  to  act  independ- 
ently with  a  high  vapor  tension  and  permits  the  temperature  to 
be  raised  beyond  the  melting  point  of  zinc  without  its  becoming 
molten.  Therefore,  the  percentage  of  inert  material  in  the  zinc 
dust  plays  an  important  part  in  the  process. 

Since  the  process  of  Sherardizing  is  being  carried  on  all  over  the 
country  under  different  conditions  and  for  different  purposes,  it  is 
impossible  to  give  any  specific  rules  for  Sherardizing.  The  follow- 
ing suggestions,  however,  can  be  applied  in  general  to  all  plants 
using  this  process. 

The  process  of  Sherardizing  can  be  divided  into  the  following 
steps  or  stages,  each  of  which  has  a  definite  relation  to  the  whole: 

1.  Inspection. 

2.  Equipment. 

3.  Zinc  dust. 

4.  Cleaning  or  preparing  of  surface. 

5.  Temperature  and  Time. 

As  said  before,  the  articles  to  be  Sherardized  cannot  be  selected 
without  increasing  their  cost,  but  this  does  not  mean  that  every- 
thing can  be  Sherardized.  If  the  article  is  excessively  corroded  or 
covered  by  inburned  slag  (sometimes  found  with  malleable  iron) 


232  GALVANIZING  AND  TINNING 

to  such  an  extent  that  ordinary  methods  of  cleaning  will  not  re- 
move it,  it  will  not  be  advisable  to  attempt  Sherardizing.  In  this 
case  such  articles  should  be  removed  on  inspection.  Many  people 
were  of  the  opinion  when  taking  up  this  process  that  anything 
would  Sherardize  regardless  of  the  condition  of  the  surface,  and 
this  is  the  prime  cause  of  the  dissatisfaction  at  the  introduction  of 
the  process. 

Just  as  in  the  electro  galvanizing  and  the  hot  galvanizing  proc- 
esses, so  in  Sherardizing,  the  surfaces  must  be  thoroughly  cleaned. 
A  hot  galvanizer  or  an  electroplater  would  not  think  of  galvanizing 
an  article  that  was  not  free  from  scale,  rust,  grease,  dirt  or  other 
impurities,  and  it  is  also  important  that  this  is  done  in  Sherard- 
izing, if  satisfactory  results  are  desired. 


CHAPTER  XXV 

Location  and  Equipment  of  the  Sherardizing  Plant 

WHILE  the  Sherardizing  business  can  be  carried  on  in 
almost  any  kind  of  a  building,  the  floors  should  be  of 
cement  or  brick  as  a  safeguard  against  the  excessive  heat 
of  the  Sherardizing  cylinders  or  drums.  Outbuildings  of  one  story 
are  preferable,  as  it  is  entirely  practicable  to  combine  the  pickling 
and  cleaning  with  the  Sherardizing.  While  the  space  required  for 
a  complete  Sherardizing  plant  varies  according  to  the  demands  and 
volume  of  work  to  be  handled,  a  plant  of  a  daily  capacity  of  one 
ton  for  treating  miscellaneous  articles,  such  as  bolts,  screws,  nails, 
chain,  stampings,  etc.,  can  be  carried  on  very  comfortably  in  a  floor 
space  of  600  square  feet. 

Little  can  be  said  in  regard  to  equipment  unless  the  articles  to 
be  Sherardized  are  determined.  If  there  are  bolts,  nuts,  washers, 
stampings,  forgings  or  articles  of  malleable  cast  iron,  the  equip- 
ment would  be  very  different  than  in  the  case  where  large  railroad 
material,  structural  iron,  etc.,  are  treated,  or  where  continuous 
Sherardizing  is  applicable,  as  with  wire,  woven  wire  cloth,  nails, 
sheet  metal,  chains,  etc. 

Fig.  101  is  a  typical  layout  of  a  floor  plan  showing  positions  of 
an  actual  Sherardizing  plant.  The  general  equipment  of  an  ordinary 
Sherardizing  plant  consists  of  a  furnace,  drums,  transfer  trucks, 
R.  E.  track,  cooling  frame,  pyrometer,  dust  screening  machine,  ash 
cans  for  holding  zinc,  loading  frame,  "I"  beam,  carriage  and  hoist, 
drum  pulling  machine,  pickling  tubs,  tumbling  barrels  and  sand 
blasting  outfit. 

The  old  pickling  tanks  which  are  now  used  almost  exclusively  for 
galvanizing  work  consist  of  four  large  wooden  tanks  set  end  to  end 
and  one  iron  tank.  Each  tank  has  a  water  and  steam  inlet  and 
a  drain  pipe.  The  new  pickling  tanks  are  used  for  Sherardizing 
work  and  consist  of  eight  small  tanks  set  in  a  row  in  groups  of 
two.  The  first  tank  contains  potash,  the  second  hot  water,  the 
third  hydrofluoric  acid,  the  fourth  hot  water,  the  fifth  sulphuric 
acid,  the  sixth  hot  water,  the  seventh  lime  water  and  the  eighth 
hot  water.  Each  tank  is  equipped  with  a  steam  and  water  inlet 

233 


234 


GALVANIZING  AND  TINNING 


and  a  drain  while  the  hot  water  tanks  also  have  overflow  pipes. 
An  electric  hoist  running  on  a  Coburn  track  runs  over  the  pickling 
tanks  and  is  used  to  lift  the  baskets  of  material  from  one  tank  to 
another.  A  sand  tumbler  is  also  used  to  clean  the  material  to  be 
Sherardized. 

h     --so'-  — *i 


RR. 
Track 


Screening 
Machine 


Shipping 


Receiving 


Picklinq  Tubs 

I lor^iooi — i 


FIG.  101.     FLOOR  PLAN  OF  SHERARDIZING  PLANT 

The  Sherardizing  Furnace  or  Oven 

There  are  several  different  styles  of  Sherardizing  ovens  or  fur- 
naces in  use, which  will  hold  one  or  more  drums,  according  to  the 
capacity  required. 

Coke   Burning  Furnace 

Figs.  102  to  106  show  the  type  of  a  coke  burning  furnace  designed 
by  A.  F.  Schoen  of  the  New  Haven  Sherardizing  Co.  This  furnace 
is  especially  valuable  in  suburban  districts  where  no  other  fuel  is 
available.  The  furnace  is  built  of  9"  fire  brick  walls  reinforced 
with  steel  plates;  has  individual  damper  controls  so  that  the 
heat,  which  passes  between  two  arching  bridges,  can  be  directed  to 
either  the  front  or  the  rear  of  the  furnace.  It  is  built  on  the  down 
draft  principle,  the  heat  passing  directly  over  and  on  top  of  the 
drums.  A  baffle  plate  is  dropped  about  6"  below  the  inlet  and  uni- 
formly distributed  in  the  furnace.  The  surplus  heat  is  then  taken 
off  underneath  the  floor  and  passes  out  under  the  furnace  diagon- 
ally, making  a  super-heating  furnace.  Owing  to  the  fact  that  the 


LOCATION  AND  EQUIPMENT  OF  SHERARDIZING  PLANT     235 


FIG.  102.    VIEW  OF  COKE  BURNING  FURNACE  OF  THREE-DRUM  CAPACITY 


FIG.  104.    FRONT  ELEVATION  OF  THREE-DRUM  COKE  BURNING  FURNACE 


236 


GALVANIZING  AND  TIXXIXG 


FIG.  103.     ANOTHER  VIEW   OF  SAME  FURNACE, 
SHOWING  OPERATING  DEVICES 


_i 
E-^:±:::::::::z::::=5;^v=-=::::z:::;::d 

FIG.   105.    SIDE  ELEVATION  OF  THREE-DRUM  COKE  BURNING  FURNACE 


LOCATION  AND  EQUIPMENT  OF  SHERARDIZING  PLANT     237 

heat  strikes  the  drums  on  the  upper  side,  it  has  been  found  that 
the  work  must  rotate  more  constantly  than  is  necessary  in  a 
gas  and  oil  burning  furnace.  Under  these  conditions  it  is 
necessary  to  have  an  automatic  rotating  device. 


FIG.  106.    SECTION  OF  THREE-DRUM  COKE  BURNING  FURNACE  TAKEN 
ABOVE  FIREBOX 

The  details  of  construction  are  clearly  shown  in  the  elevations 
and  sectional  drawings  given  in  Figs.  104,  105  and  106. 

Single  Drum  Coke  Burning  Furnace 

Fig.  107  illustrates  a  single  drum  coke  burning  furnace  also 
built  by  Mr.  Schoen.  It  is  reinforced  on  three  sides  with  steel 
plate,  with  an  inner  lining  of  9  inches  of  firebrick  and  single  arch. 
A  feature  of  this  furnace  is  that  it  can  be  grouted  so  as  to  bring 
the  door  proper  in  line  with  floor,  which  obviates  the  necessity 
of  a  transfer  car.  This  also  applies  to  furnace  in  Fig.  102.  The 
grouting  can  only  be  done  on  the  ground  floor.  The  details  of 
construction  and  general  operation  are  clearly  shown  on  the  floor 
plans  and  elevations  given  in  Figs.  108,  109  and  110.  This  fur- 
nace can  be  lengthened  to  eight  feet  long  and  operated  uniformly 
from  a  three-foot  firebox. 


238 


GALVANIZING  AND  TINNING 


Note  the  drum  turning  device  through  furnace  door.  This  was 
necessary  through  lack  of  room  in  rear  of  furnace  at  which  point 
all  rotating  devices  are  generally  attached. 

Controlling  Heat  of  Single  Arching  Furnace 

Unlike  the  double  arching  furnace,  which  forms  a  pocket  from 
which  the  flame  and  heat  are  uniformly  forced  into  the  furnace, 


FIG.  107.   SINGLE-DRUM  COKE  BURNING  FURNACE 

in  a  single  arch  furnace  it  comes  directly  over  the  inner  wall  as 
shown  in  Fig.  101),  and  the  flame  therefore  has  a  tendency  to  go 
to  the  rear  of  the  furnace  even  though  the  exhausts  are  at  the  front. 


LOCATION  AND  EQUIPMENT  OF  SHERARDIZING  PLANT     239 

This  is  overcome  by  tapering  the  outlet  or  baffling  the  brick  at 
various  points.  A  baffle  plate  is  attached  to  the  arch  directly  over 
the  drum  to  brake  the  flame  and  direct  the  heat  so  it  will  be  uni- 
formly distributed  around  the  drum  or  receptacle. 

Gas  and  Oil  Burning  Furnaces 

Fig.  Ill  illustrates  a  small  self -contain  ing  furnace  built  of  struc- 
tural iron  and  brick,  with  the  (over  attached  by  hinges,  lined  with 


L, -2' 5-— -i 

FIG.  108.    FRONT  ELEVATION  OF  SINGLE-DRUM  COKE  BURNING  FURNACE 


FIG.  109.    SIDE  ELEVATION  OF  SINGLE-DRUM  COKE  BURNING  FURNACE 


240 


GALVANIZING  AND  TINNING 


fire  brick  and  fire  clay  on  the  inside  for  gas  or  oil  burning. 
The  material  Sherardized  in  this  oven  would  probably  be 
bolts,  nuts,  washers,  small  malleable  cast-iron  articles,  small 


671- 


&Q&- 

FIG.  110.    SECTION  OF  SINGLE-DRUM  COKE  BURNING  FURNACE 


FIG.  111.    A  SELF-CONTAINED  GAS  FURNACE  AND  DRUM 

castings  and  forgings  and  all  small  or  medium  sized  iron  or 
steel  pieces  that  would  pass  through  an  opening  10x;$(>  in.  A 
special  feature  of  a  furnace  of  this  kind  is  that  it  can  be  placed 


LOCATION  AND  EQUIPMENT  OF  SHERARDIZING  PLANT     241 

anywhere  in  the  factory  and  operated  at  very  little  expense,  re- 
quiring no  elaborate  equipment  in  handling,  and  is  very  convenient 
even  in  the  factories  where' large  Sherardizing  plants  are  in  opera- 
tion, due  to  the  fact  that  small  special  work,  which  could  not  be 


FIG.  112.   GAS  BURNING  FURNACE  USED  BY  NEW  HAVEN  SHERARDIZING  Co. 

run  in  furnaces  where  two  and  three  cylinders  were' operating  at 
one  time,  can  be  taken  care  of. 

Fig.  112  illustrates  the  type  of  gas  burning  furnace  used.  This 
style  of  furnace  is  also  operating  successfully  with  natural  gas, 
producer  oil  and  fuel  oil. 

Figs.  113  to  114  are  detailed  sectional  views  of  gas  and  oil  burn- 
ing furnaces.  You  will  note  that  the  only  difference  between  the 
two  furnaces  is  that  the  combustion  chamber  for  the  oil  is  more 
thoroughly  reinforced  at  the  floor  lines,  the  combustion  taking 


242 


GALVANIZING  AND  TINNING 


place  between  the  floor  and  the  upper  baffle  bricks  and  coming 
out  at  the  sides.  The  gas  burning  is  an  open  flame  directly  against 
the  drums,  taking  air  from  underneath'  the  furnace,  the  air  fol- 
lowing along  the  burners.  This  applies  where  no  pressure  is  used. 
In  cases  where  gas  is  used  under  pressure  then  use  the  same  equip- 


Door  Hast 


,.  -  Angle  Iron  for  Gas  Burning  onfy 

,  4'Tile  for  Oil 
Burning  only 


2'  Space  behvee 
Baffles 


O: 


t± 


-  -2" Pipe        ^Baffle  Brick  ibr  Oil  Burners' 


FIG.  113.    SECTION  OF  FURNACE  SHOWING  DIFFEKEXCE  IN  KEINFOKCING  OF 
COMBUSTION  CHAMBER  FOR  GAS  AND  OIL 


"i 

k_ 

1      0) 

ii 

T 

• 

s& 

:'!' 

i  j 

1 

lu  

-1L-I 

.  _  Jj-. 

1 

•1 

i 

f 

1         (? 
1        5 

i 

i 

1      £ 

i 

i 

ft) 

1      V 

:> 

i 

Iri  '- 

! 

4- 

i 

Baffle 
7/,fe 
>n3 
Sections 

! 

h 

|| 

1 

'i  'i 

1  1 

1 
1 

| 

l! 

Gas  Cocks 

FIG.  114.    PLAN  OF  FURNACE  SHOWING  ARRANGEMENT  OF  COMBUSTION 
CHAMBER  FOR  GAS  AND  OIL 


LOCATION  AND  EQUIPMENT  OF  SHERARDIZING  PLANT    243 


244  GALVANIZING  AND  TINNING 

ment  as  for  oil,  allowing  more  relief  from  the  combustion  chamber 
or  a  slight  baffle  which  will  distribute  the  fiame  uniformly. 

As  shown  in  Fig.  113,  an  angle  iron  is  to  be  used  for  gas  burning 
at  that  point  only;  for  fuel  oil,  which  gives  off  great  heat  and  back 
pressure  at  intake,  would  quickly  warp  any  metal  parts  and  render 
it  useless  as  a  frame  support.  A  tie  rod  at  the  floor  line  well  pro- 
tected with  bricks  is  recommended. 

Fig.   115  shows  a  furnace  in  the  plant  of  the  American  Tap 


FlG.   116.    TWO  COMPABTJIENTS  OF  THE  FURNACE  SHOWN  IN  FlG.    115   READY 

TO  RECEIVE  THE  DRUMS 


Brush  Co.,  of  Detroit,  Mich.,  which  has  a  capacity  of  twenty  tons 
per  day.  The  drums  are  5'  long,  18"  in  diameter,  and  the  furnace 
is  so  built  with  separate  chambers  that,  if  the  treatment  of  longer 
material  was  required,  they  would  simply  have  to  couple  the  drums 
together  to  any  desired  length.  This  plant  would  be  a  valuable 
plant  to  any  one  doing  jobbing  work  and  having  a  variety  of  ma- 
terial to  be  treated  in  different  lengths. 

Fig.  116  shows  two  compartments  of  the  furnace  ready  to  receive 
an  11^  ft.  drum.  It  also  shows  the  method  of  turning  the  drums 
and  the  combustion  chamber. 


LOCATION  AND  EQUIPMENT  OF  SHERARDIZING  PLANT    245 


FIG.  117.     A  FUEL  OIL  BURNING  FUBNACE  OF  FOUK-DHUM  CAPACITY 


FIG.  118.   TYPE  OF  OIL  BURNING  FURNACE 


246 


GALVANIZING  AND  TINNING 


LOCATION  AND  EQUIPMENT  OF  SHERARDIZING  PLANT    24? 


248  GALVANIZING  AND  TINNING 

Fig.  117  is  a  view  of  the  John  Finn  Metal  Co/s  plant,  in  San 
Francisco.  This  is  a  fuel  oil  burning  furnace  of  four  drum  ca- 
pacity. The  drums  are  rotated  by  a  reciprocating  movement  of 
the  carriage  from  one  end  of  the  furnace  to  the  other.  Consider- 
able space  could  have  been  saved  in  this  furnace  by  installing  a 
pivot  motion. 

The  pivot  motion  is  shown  in  Fig.  118,  which  illustrates  the  type 
of  furnace  used  by  the  Westinghouse  Electric  and  Mfg.  Company 
and  the  Union  Switch  and  Signal  Company.  This  furnace  was 
installed  for  oil  fuel,  but  there  is  no  reason  why  it  may  not  be 
used  for  gas,  producer  gas  or  natural  gas.  All  that  is  necessary  is 
to  change  the  inside  floor  plans  to  provide  the  desired  combustions. 

Figs.  119  and  120  show  the  loading  and  cooling  platforms 
of  a  furnace  operated  by  the  National  Metal  Molding  Co., 
of  Pittsburg,  for  treating  conduit  pipe  and  conduit  fit- 
tings, and  has  a  capacity  of  about  thirty-five  tons  per  clay.  This 
type  of  furnace  is  also  recommended  for  water  pipe  and  tubing. 
The  drums  are  automatically  taken  into  the  furnace  on  very  heavy 
chains  and  are  automatically  rotated  with  a  sprocket  attached  to 
the  center  of  the  drum,  the  chain  passing  beneath  with  a  continu- 
ous movement  and  protected  from  the  flame. 


FIG.   121.    SERIES  OF  ELECTRIC  HEATED  SHERARDIZING  MACHINES 

Electrically  Heated  Furnaces  or  Drums 

A  new  departure  in  the  Slierardizing  field  is  the  special  type 
of  electrical  heated  apparatus  designed  for  the  General  Electric  Co. 
This  company  coats  considerable  malleable  iron  and  they  are  now 


LOCATION  AND  EQUIPMENT  OF  SHERARDIZIXG  PLANT     249 


•I 


FIG.  122.    24"  x  24"  x  40"  ELECTRIC  HEATED  SHERARDIZING  MACHINE 
i.\  OPERATION 


FIG.  123.    LAYOUT  FOR  WIRING  OF  ELECTRIC  HEATED  SHERARDIZING 

MACHINE 


&0  GALVANIZING  AND  TINNING 

using  two  sizes  of  machine;  one  10"  x  10"  x  1?"  inside  dimensions 
and  requiring  15  kw.  to  bring  up  to  the  desired  temperature  and 
5  kw.  to  hold  correct  temperature,  and  a  larger  one  24"  x  24"  x  40" 
inside  dimensions  requiring  LQ  kw.  to  heat  up  and  15  to  hold 
at  that  temperature.  The  former  is  illustrated  in  Fig.  121  and  the 
latter  is  shown  with  connections  for  heating  in  Fig.  122. 

It  will  be  noted  that  the  machines  are  rectangular  in  shajK'  ami 
are  revolved  by  a  driving  motor  mounted  on  one  of  the  pedestals 
and  geared  to  the  drum  through  a  reduction  worm  gear.  The 
heating  elements  are  placed  on  each  of  the  four  sides  and  both 
ends  of  the  machine,  and  the  current  is  supplied  to  them  through 
three  collector  rings  at  one  end  of  the  machine. 

Wiring  Diagram 

The  connections  are  such  that  the  drum  can  be  operated  on  a 
three-wire  250/125  volt  B.C.  circuit  or  a  three-phase  A.C.  circuit. 
The  only  change  necessary  for  a  three-phase  A.C.  circuit  is  to 
leave  off  the  wire  leading  to  the  bottom  middle  clip  of  the  T.P.  D.T. 
switch. 

The  general  scheme  of  inside  and  outside  wiring  for  the  two 
drums  may  be  seen  in  Fig.  123.  This  layout  is  for  a  250/125  volt 
D.C.  circuit. 

Drums 

The  requisite  number  of  drums  or  containers  can  be  made  in 
either  cylinder,  square  or  flat,  suitable  for  material  to  be  treated. 
For  instance,  small  articles  that  can  be  handled  readily  with  a 
shovel  or  chain  in  bundles  it  is  best  to  treat  in  a  round  cylinder, 
averaging  from  15"  to  20"  in  diameter  and  up  to  6'  long.  It  is 
not  necessary  to  make  these  drums  out  of  heavier  than  i/t"  boiler 
plate,  as  there  is  no  actual  wear  in  the  low  degree  of  heat  main- 
tained. It  has  been  known  that  drums  in  daily  use  up  to  eight 
years  show  practically  no  wear  and  are  as  good  as  new. 

A  Mjiiare  drum  is  used  a  great  many  times  for  light  material, 
and  a  top  opening  cover  is  recommended  instead  of  an  opening  at 
the  ends.  This  will  allow  perfect  packing,  so  that  when  the  articles 
are  taken  out  they  will  not  be  bent  or  warped.  It  is,  however, 
recommended  that  drums  not  over  20"  square  be  used  on  such  light 
material  to  insure  uniform  penetration.  In  the  case  of  flat  >t<>, -k 
for  panel  work,  etc.,  a  flat  drum  of  not  over  16"  in  depth  is 
recommended,  as  the  stock,  being  flat,  will  lie  very  closely  and  it 


LOCATION  AND  EQUIPMENT  OF  SHERARDIZING  PLANT     251 

would  be  impossible  to  get  a  perfect,  uniform  coating  if  the  diameter 
was  increased.    The  length  and  width  make  no  difference. 

Fig.  124  illustrates  a  cylinder  drum  15"  to  20"  in  diameter,  made 
of  14"  boiler  plate,  welded.  The  flange  and  head  are  cast  or 
malleable  iron  and  are  machined  to  make  a  dust  proof  fit.  There 
is  one  feature  that  deserves  special  attention.  It  is  the  use  of 
slotted  parts  instead  of  holes  for  fastening  on  the  heads.  Ordi- 
narily the  bolt  will  expand  with  the  heat  to  such  an  extent  that  it 
is  impossible  to  remove  the  nut,  but  with  the  above  arrangement 
the  bolt  can  be  removed  without  injury,  or  where  the  nut  will  not 
come  off  it  will  loosen  sufficiently  to  work  out  of  the  slot. 


FIG.  124.   A  CYLINDER  DRUM 

Dust  Separating  Machine 

Fig.  125  gives  a  sectional  view  of  a  dust  separating  ma- 
chine. This  screener,  which  is  known  as  a  cylinder  screener, 
is  made  of  structural  angle  iron,  2y2"  x  14",  and  matched 
boards,  thoroughly  reinforced,  and  the  screen  is  made  of  per- 
forated metal.  The  work  is  received  at  one  end,  the  dust 
dropping  through  into  a  receiving  box  and  the  material  com- 
ing through  at  the  other  end  free  from  dust.  It  has  been  found, 
in  a  good  many  instances,  that  on  flat  stock  or  cup-shaped  material 
the  dust  is  not  all  relieved  at  the  first  screening,  in  which  case  a 
conveyer  is  made  of  two  pieces  of  5"  x  5"  angle  iron  and  a  carrying 
belt  is  placed  on  the  receiving  end  of  the  screen  and  conveyed  to 
another  screening  machine  of  the  same  type,  which  will  relieve 
such  zinc  as  has  passed  through  the  first  screener.  A  conveyer  of 


252  GALVANIZING  AND  TINNING 

this  type  is  very  easily  constructed  and  inexpensive,  and  saves  a 
lot  of  shoveling  and  handling.  The  gear  pattern  is  so  arranged 
that  it  can  be  operated  with  worm  drives. 

Fig.  125  illustrates  the  style  and  make  of  dust  separating  machine 
used.  This  screen  can  be  placed  anywhere  on  the  floor,  no  pits  or 
conveying  device  necessary.  The  machine  will  hold  about  three 
thousand  pounds  of  zinc  at  one  screening. 


FIG.  125.   DUST  SEPARATING  MACHINE 

Mr.  Schoen  of  the  New  Haven  Sherardizing  Co.  has  spent  a 
numter  of  years  perfecting  this  machine,  and  believes  that  a  ma- 
chine of  this  type  should  be  part  of  the  equipment  of  every  plant, 
for  it  is  inexpensive  and  turns  out  clean  work.  An  exhaust  hood 
should  be  attached  to  carry  all  zinc  residue  to  the  reclaiming  box. 

Fig.  126  shows  this  same  screener  in  operation,  receiving  the  Avork 
from  the  drum ;  also  a  hood  placed  in  such  a  position  that  the  light 
zinc  dust,  which  is  bound  to  fly,  is  taken  care  of  under  a  slight  suc- 
tion. The  drum  is  conveyed  by  means  of  an  overhead  trolley.  The 
head  is  removed  from  one  end  of  the  drum  and  the  material  is 


LOCATION  AND  KQUIPMENT  OF  SHERARDIZING  PLANT     253 

dumped  into  the  hopper.  The  screen  revolves  about  forty  revolu- 
tions per  minute,  the  dust  dropping  through  into  the  receiving  box 
below  and  the  material  coming  out  at  the  other  end.  A  hood  is 


FIG.    12(5.    DUST   SCHEENER  IN   OPERATION 


placed  over  the  receiving  hopper  at  the  end  where  the  material 
comes  out ;  an  exhaust  is  attached  with  enough  suction  to  take  care 
of  whatever  dust  may  escape.  This  is  exhausted  into  a  canvas- 
covered  box  and  saved. 

The  Transfer  Car 

The  transfer  car  is  not  of  any  special  make.  It  is  merely  usnl 
for  transferring  drums  from  one  place  to  another  and  can  be 
easily  built  from  structural  iron  with  a  few  cast-iron  wheels  and 
bearings,  thoroughly  reinforced.  Generally  speaking,  these  are 
specially  manufactured  to  meet  the  requirements  of  different  plants. 
Fig.  127  shows  one  type  of  truck  used.  The  "I"  beam  is  standard, 
generally  using  the  very  lightest,  as  the  weight  ordinarily  carried 
in  one  of  these  drums  is  not  over  one  ton. 


254  GALVANIZING  AND  TINNING 

Fig.  127  also  show-;  three  drums  placed  in  position  and  secured  by 
a  locking  frame,  which  keeps  the  drums  the- right  distance  apart 
and  transforms  same  into  a  track.  They  are  standard  cylinders 


FIG.  127.    TRANSFER  CAR  AND  DRUMS 


FIG.  128.   ROLLING  DRUMS  INTO  FURNACE  AS  A  UNIT 


LOCATION  AXD  EQUIPMENT  OF  SHERARDIZING  PLANT     255 

with  gears  attached  to  drum  heads.  The  driving  gear  coming  at 
the  rear  end  inside  of  the  furnace,  as  shown  in  Fig.  103,  turns  all 
three  drums  uniformly,  as  they  are  all  interlocked.  These  can  also 
be  operated  individually  without  gears,  as  shown  in  Fig.  128. 

NOTE. — The  wheels  placed  loosely  on  the  hub  act  as  a  bearing  and 
truck.  This  method  is  recommended,  as  it  obviates  the  necessity  of 
using  heavy  structural  iron  trucks,  which  mean  an  additional 
expense  for  heating  of  additional  iron  and  also  the  trouble  of  keep- 
ing the  truck  from  warping. 

Fig.  128  illustrates  furnace  receiving  drums  from  the  transfer 
car. 

This  operation  is  handled  mechanically  by  a  pulling  device'  at 
the  rear  of  the  furnace;  but  as  extra  large  bearings  are  used,  one 
man  can  easily  push  the  drums  into  the  furnace:  In  case  of  in- 
dividual rotating  or  turning  the  stems  as  shown  are  then  pushed 
into  the  hub  of  the  drum,  which  also  holds  the  drums  in  position. 
AVith  gear  drive  they  are  locked  into  position  with  a  clutching 
device  on  the  track  at  the  front  of  the  drums. 

Cooling  Frames 

Cooling  frames  need  no  special  specifications.  Two  pieces  of 
railroad  track  or  channel  iron,  mounted  so  that  they  meet  the 
transfer  truck,  are  all  that  is  necessary. 

Pyrometers 

Every  furnace  should  be  equipped  with  a  pyrometer,  which  is 
placed  on  the  wall  in  the  operating  room,  a  certain  distance  away 
from  the  furnace,  and  thoroughly  protected  in  a  dust-proof  case. 
The  leads  can  be  bought  any  length  to  go  with  the  instrument,  and 
are  always  standard.  Recording  instruments  are  highly  recom- 
mended. Chapter  III  gives  special  attention  to  pyrometers. 


CHAPTER  XXVI 

Materials  Used  in  Sherardizing 

CONCERNING  the  practical  side  of  Sherardizing,  the  arti- 
cle to  be  Sherardized  must  be  regarded,  first,  in  respect  to 
its  ability  to  absorb  zinc  vapor,  and  then  the  condition 
under  which  zinc  produces  vapor  at  the  highest  tension. 

The  articles  to  be  Sherardized  are  almost  exclusively  of  iron  in 
its  different  stages  and  forms,  as  cast  iron,  malleable  iron,  wrought 
iron,  cold-rolled  steel  and  steel  in  all  its  stages.  Many  kinds  of 
iron  articles  have  to  be  dealt  with  in  many  forms  and  stages  and 
quite  naturally  they  would  have  different  rates  of  occlusion,  due  to 
the  nature  of  the  structure  and  form  and  quality  of  surface.  The 
articles  to  be  Sherardized  cannot  be  selected  to  any  extent  and  the 
specifications  under  which  the  articles  are  being  made  cannot  be 
changed  without  affecting  their  cost.  Therefore,  the  most  favor- 
able condition  under  which  the  given  article  Avill  absorb  the  most 
zinc  vapor  must  be  obtained.  In  some  cases  it  will  be  a  selection 
of  temperature  or  pressure:  in  some  cases >it  will  be  the  treatment 
of  the  article,  as  annealing,  or  annealing  under  a  reducing  atmos- 
phere, and  in  some  cases,  in  the  treatment  of  the  surface  mechani- 
cally (sand  blasting  and  tumbling),  or  chemically  (pickling). 

In  the  theoretical  discussion,  mention  was  made  of  the  effect  of 
temperature  as  an  important  factor  to  both  elements  of  the  process. 
In  this  connection  it  would  be  well  to  note  that  a  critical  point 
exists  for  the  articles  Sherardized,  for  not  all  articles  to  be  Sher- 
ardized could  be  heated  to  the  same  degree  without  changing  their 
physical  properties.  From  this  we  see  that  the  definite  temperature 
for  each  special  condition  must  be  determined,  which  is  best  for 
both  the  zinc  dust  and  the  treated  article. 

The  material  used  in  the  process  of  Sherardizing  is  commercial 
zinc  dust,  commonly  called  blue  powder,  of  which,  at  this  time, 
about  90%  is  imported  and  which,  as  an  average,  runs  from  75% 
to  90%  metallic  zinc.  Grasselli  zinc  is  also  used,  but  mostly  in 
keeping  up  the  strength  after  the  zinc  has  been  reduced  to  a  low 
percentage.  This  is  made  from  ground  spelter  and  must  be  run 

256 


MATERIALS  USED  IN  SHERARDIZING  257 

at  a  much  lower  degree  of  heat  than  the  blue  powder.  Zinc  dross 
is  also  used,  but  not  very  successfully,  as  it  will  not  alloy  itself  with 
the  work  as  thoroughly  as  the  finely  powdered  zinc,  although  when 
the  two  are  combined  in  equal  parts  they  show  very  good  results. 

Dust  from  the  Zinc  Smelter 

There  are  two  kinds  of  zinc  dust  on  the  market  for  commercial 
purposes,  Grasselli  and  common  blue  dust.  Blue  dust  is  a  by- 
product of  a  zinc  smelter  and  is  mostly  imported  from  Belgium  and 
Germany.  Grasselli  dust  is  manufactured  in  this  country  from 
metallic  zinc.  The  zinc  dust  should  be  kept  dry,  and  if  new  zinc 
dust  is  used  it  should  be  dried  out  for  several  hours  in  the  Sher- 
ardizing  drums  at  100  deg.  C.,  slowly  rising  up  to  250  deg.  C. 

The  blue  dust  can  be  used  with  a  lower  metallic  percentage.  Less 
time  is  required  for  the  run  in  the  oven  (5  to  6  hours).  The  quality 
of  coating  is  better,  as  it  is  more  uniform  and  solidified.  Black 
spots  are  practically  eliminated.  There  is  no  danger  of  fusion, 
bailing,  balling,  and  caking,  irrespective  of  the  various  high  tem- 
peratures. High  temperatures  can  be  used. 

The  drums,  however,  cannot  be  opened  when  using  blue  dust 
until  a  relatively  low  temperature  has  been  reached,  due  to  the 
very  quick  oxidation  and  danger  of  ignition.  A  longer  period  is 
therefore  required  for  cooling.  There  are  difficulties  of  handling 
this  dust  without  a  proper  ventilating  system  and  adhesion  of 
loose  dust  to  threaded  and  knurled  surfaces  occurs. 

Freeing  Dust  from  Iron 

The  dust  is  run  through  a  magnetic  separator  at  least  once 
every  four  weeks  to  take  out  superfluous  small  particles  of  iron 
which  are  liable  to  become  lodged  between  the  jaws  of  cotter  pins, 
etc.,  and  thus  cause  trouble  in  assembly.  By  cleaning  the  dust  this 
way  the  mechanical  incorporation  of  large  percentages  of  iron  dust 
in  the  coating  is  also  prevented.  It  is  recommended  that  the 
weekly  analysis  of  working  dust  show  the  iron  content. 

The  Use  of  Manufactured  Zinc  Dust 

A  brighter  metallic  coating  is  obtained  than  with  the  blue  dust. 
Less  time  is  required  for  cooling  and  less  danger  is  encountered  in 
opening  the  drums  when  hot. 

A  higher  metallic  percentage  is,  however,  necessary  and  a  longer 


258  GALVANIZING  AND  TINNING 

time  is  required  for  the  run  in  the  oven.    There  is  also  danger  of 
fusion  of  zinc  due  to  slight  overrunning  of  temperature. 

Method  No.   i  for  Determining  Metallic  Zinc  in  Zinc  Dust 

Into  a  400  c.c.  Erlenmeyer  flask  weigh  10  grams  of  zinc  dust, 
to  be  investigated.  Measure  10  c.c.  of  metallic  mercury  into  same, 
add  100  c.c.  of  boiling  hot  water,  and  run  into  same  from  a  burette 
the  excess  of  standard  normal  HC1,  the  amount  added  depending 
entirely  on  the  oxide  contents  of  the  dust  under  investigation. 
(From  30  to  50  c.c.  usually  suffices  unless  the  dust  is  unusually 
high  in  oxide.)  '  After  the  excess  of  acid  is  added,  as  shown  by 
methyl  orange,  insert  a  stopper  and  shake  for  several  minutes  until 
the  metal  is  completely  alloyed,  and  the  oxide  is  dissolved,  with  the 
exception  of  a  small  amount  of  coal  dust  and  insoluble  matter 
which  usually  accompanies  such  products  After  the  solution  is 
effected,  decant  off  the  liquor  from  the  mercury  alloy,  wash  the 
alloy  by  decantation  in  the  flask,  and  titrate  the  excessive  acid 
with  standard  normal  soda  solution  until  same  is  exactly  neutral, 
as  shown  by  change  of  indicator,  as  well  as  by  faint  precipitation 
of  zinc  in  solution;  calculate  the  percentage  of  oxygen  (1  c.c.  of 
normal  HC1  being  equal  to  .008  oxygen)  from  which  the  zinc 
oxide  can  readily  be  calculated. 

1  c.c.  N2HC1  =  0.0203  gram  zinc  oxide 
Per  cent,  of  metallic  zinc  =  100%  less  %  of  zinc  oxide 

Method  No.  2  for  Determining  Metallic  Zinc  in  Zinc  Dust 

Weigh  out  exactly  0.2939  g.  of  dust  and  introduce  same  in  a 
200  c.c.  Erlenmeyer  flask.  Add  a  piece  of  Pt.  foil  as  a  catalyte. 
Add  30  c.c.  water.  Put  10  c.c.  cone.  H2S04  into  a  small  bottle 
and  lower  same  into  flask  without  spilling. 

Connect  up  flask  to  gas  burette.  Invert  flask  enough  to  mix  acid 
with  water.  After  standing  for  3  hours,  read  off  on  burette  number 
of  c.c.  hydrogen  generated  by  action  of  acid  on  zinc.  Make  correc- 
tion for  temperature.  Number  of  c.c.  gives  per  cent,  metallic  zinc. 

If,  after  having  determined  the  proper  conditions  to  get  the 
correct  results  in  Sherardizing,  these  conditions  are  held  to  during 
the  operation,  the  results  will  be  constant.  If  these  conditions  are 
allowed  to  vary  beyond  reasonable  limits,  then  the  product  will 
vary,  and  the  Sherardizing  will  be  irregular. 

It  is  my  belief  that  these  impurities  have  little  or  nothing  to  do 


MATERIALS  USED  IN  SHERARD1ZING  259 

with  the  properties  of  zinc  dust  and  that  the  reason  should  be 
sought  for  it  in  its  mode  of  production. 

Method  No.  3  for  Determining  Metallic  Zinc  in  Zinc  Dust 

To  prepare  permanganate  of  potash  titrating  solution  (it  is  not 
a  clarifying  solution)  weigh  out  5  g.  of  pure  fresh  permanganate  of 
potash  crystals — weigh  accurately — dissolve  in  500  c.c.  of  pure  dis- 
tilled water  at  60  deg.  F.  or  thereabouts,  i.e.,  upset  the  crystals  into 
a  dry  glass-stoppered  flask  and  then  fill  up  with  water  to  the  500 
c.c.  mark.  Do  not  put  the  water  in  and  then  the  crystals  after- 
wards, which  would  make  the  solution  one  or  two  per  cent,  too 
weak.  Place  glass  stopper  in  position,  shake  well  till  dissolved  and 
then  store  in  a  dark  cupboard.  It  will  keep  for  about  a  fortnight 
or  so,  but  for  competitive  or  buying  or  selling  samples,  where  ex- 
treme accuracy  is  wanted,  always  make  up  a  fresh  solution. 

Weigh  out  from  a  previously  carefully  selected  sample  of  zinc 
dust,  1  g.,  weighing  same  to  a  hair;  suspend  in  about  2  in.  of 
distilled  water  in  a  glass  beaker  3"  in  diameter — beaker  large 
enough  to  hold  a  pint.  Add  to  this  12  to  20  g.  (according  to  pre- 
sumed metallic  value  of  dust)  of  pure  ferric  sulphate,  and  stir  it 
and  grind  it  with  a  glass  rod  for  20  min.  off  and  on  till  all  the 
zinc  dust  and  all  the  ferric  sulphate  is  dissolved  with  the  exception 
of  a  few  possible  impurities  at  the  bottom.  Test  these,  however,  by 
grinding  them  with  the  glass  stirring  rod  and  hold  beaker  up  to  a 
strong  light  and  looking  through  it  from  the  bottom  and  if  any  ac- 
tion (bubbling  or  movement)  is  seen  on  these  impurities,  give  the 
solution  a  little  more  time  to  dissolve  them.  Then  add  another  inch 
or  so  of  pure  water  to  save  intense  heat  when  acidulating,  then  add 
25  c.c.  strong  sulphuric  acid  C.  P.  (for  ordinary  shop  work  good 
soft  clean  tap  water  if  free  from  organic  matter,  and  good  quality 
commercial  acid  will  do).  Stir  the  acid  in. 

Before  adding  the  acid  the  solution  is  of  a  rusty  orange  color. 
After  adding  the  acid  the  solution  is  of  a  light  emerald  color. 

Having  done  this,  take  a  100  c.c.  graduated  measuring  glass  tube, 
with  a  cock  at  the  bottom,  i.e.,  about  O1/^"  high  and  1%"  or 
less  in  diameter  and  graduated  by  centimeters  from  0  to  100  c.c., 
and  fill  it  up  to  the  100  c.c.  mark  with  the  permanganate  of  potash 
solution. 

Gradually  pour  this  into  the  zinc  solution.  At  first  the  pink 
color  will  almost  instantly  disappear,  then  go  slower  and  hang 


260  GALVANIZING  AND  TINNING 

cloudy.  Keep  stirring  all  the  time  until  the  end,  i.e.,  when  the  last 
drop  or  two  added  and  well  stirred  will  just  turn  the  whole  solu- 
tion throughout  a  pale  salmon  pink.  Then  stop.  Bead  off  from 
the  glass  how  much  of  the  solution  was  used  and  multiply  this  hy 
1.0364.  The  result  will  be  the  actual  metallic  percentage  of  the 
zinc  dust. 

Example:  49  c.c,  of  solution  used  to  give  the  pink  color.  Then 
49  X  1-0364  =  50.7836  per  cent,  metallic  zinc.  Thirty  to  40  per 
cent,  dust  will  do  with  12  to  15  g.  ferric.  Over  that  make  sure  by 
giving  it  20  g.  ferric.  Excess  does  not  harm. 


CHAPTER  XXVII 

Preparing  Material  and  Loading 

THE  methods  described  in  the  preceding  pages  of  this  book, 
for  cleaning  castings  and  other  material  for  hot  galvaniz- 
ing and  tinning,  are  also  applicable  to  material  for  Sherard- 
izing  with  the  following  exceptions.  When  cleaning  with  acid  by 
the  pickling  process,  the  acid  should  be  thoroughly  relieved. 

If  a  sufficient  amount  of  cast  and  malleable  cast  iron  are  handled 
it  might  be  advantageous  to  use  a  sand  blast  for  removing  the  dirt, 
rust  or  slag,  but  when  castings  form  only  a  part  of  the  work 
they  can  be  treated  according  to  the  following  specifications. 

Cleaning  material  by  sand  blasting  is  accomplished  by  subject- 
ing the  material  to  the  impact  of  fine,  clean,  dry  sand  under  air 
pressure  of  20  to  80  pounds.  If  the  work  to  be  cleaned  consists 
of  large  pieces  that  can  be  handled  easily,  hose  about  14  to  %" 
is  used.  If  the  material  consists  of  small  articles  it  is  more  eco- 
nomical to  use  a  sand  blast  tumbling  barrel.  The  advantage  of 
cleaning  material  by  this  "method  is  that  all  slag  or  silica  scale  is 
quickly  removed,  exposing  the  clean  iron.  It  also  overcomes  the 
use  of  acids,  etc.,  which  are  very  hard  to  eliminate  in  porous  or  bad 
castings.  A  comprehensive  treatment  of  sand  blasting  and  clean- 
ing in  the  tumbling  barrel  is  given  in  Chapter  VI. 

Pickling  of  Steel 

In  pickling  steel,  such  as  bolts,  nuts,  washers  and  scaly  material, 
the  articles  should  be  thoroughly  washed  in  the  lye  solution,  the 
strength  of  which  must  be  about  38  pounds  of  lye  to  each  100  gal- 
lons of  water.  Care  must  be  taken  that  no  washcd-off  oil  or  fat 
is  allowed  to  float  in  the  tank,  and  skim  as  frequently  as  possible. 
When  the  solution  becomes  greasy  or  brownish  in  color,  it  should 
be  renewed.  If  the  tank  is  to  be  kept  busy,  the  renewal  should  take 
place  every  other  day.  Keep  the  material  in  the  solution  from  5  to 
10  minutes,  and  drain  in  the  basket.  If  the  material  is  covered 
with  dried-out  oil,  it  should  remain  in  the  solution  for  a  longer 
time. 

261 


262  -  GALVANIZING  AND  TINNING 

Wash  in  hot  water  and  drain. 

Place  in  the  hot  sulphuric  acid  solution  long  enough  until  all 
foreign  substance  has  been  removed  or  dissolved  (in  some  cases 
5  to  8  minutes).  The  strength  of  this  sulphuric  acid  solution 
should  be  about  9.5  per  cent.,,  in  which  13  gallons  of  66  per  cent, 
commercial  sulphuric  acid  solution  should  be  used  to  each  76.5  gal- 
lons of  water.  The  pickling  qualities  of  this  solution  can  be  de- 
termined by  its  density  and  its  color.  A  hydrometer  should  be 
used  and  the  point  ion  should  he  about  1.115  at  38  deg.  C.,  or 
about  1.110  at  80  dog.  C.  If  the  solution  should  happen  to  be 
clear  and  its  density  less  than  the  stated  value,  acid  should  be 
added  to  maintain  its  strength.  Jf  the  color  of  the  solution  changes 
and  appears  brownish,  the  solution  becomes  invalid  and  should  be 
renewed.  Drain  the  material  in  tbis  solution. 

Wash  in  hot  water  and  diain. 

Place  in  a  lime  solution,  which  will  neutralize  any  acid  that  still 
remains  on  the  material.  The  strength  should  be  about  20  pounds 
of  either  quicklime  or  air  slacked  lime  to  each  100  gallons  of 
water.  When  the  solution  changes  from  a  milky  to  a  brownish 
color  it  should  be  renewed.  The  material  should  remain  in  this 
lime  solution  for  at  least  5  minutes  and  then  drain. 

Wash  in  hot  water  and  drain.  From  time  to  time  litmus  tests 
should  be  made  in  this  water  tank,  and  when  the  water  shows  acid 
reaction  it  should  be  renewed.  Jn  case  flaky  sediments  occur  in 
this  tank,  it  is  advisable  that  the  drain  be  opened  at  different 
periods  to  remove  them,  since  they  are  heavier  than  water  and 
cannot  be  washed  out  by  the  inflowing  water.  Usually  the  tank 
may  be  drained  twice  a  day.  . 

Empty  the  material  on  the  inclined  screen  for  drying. 

The  temperature  of  the  acid  and  alkali  solutions  should  be  60 
deg.  to  80  deg.  C. 

The  temperature  of  the  water  baths  should  be  70  deg.  to  90 
deg.  C. 

Fresh  running  water  should  be  allowed  to  enter  each  water  tank 
in  order  to  keep  it  clean. 

Before  each  renewal  of  either  water,  acid  or  alkali  solution,  the- 
tank  should  be  thoroughly  cleansed. 

During  the  pickling  process  the  baskets  of  material  should  be 
shaken  and  dipped  several  times  into  the  solution  in  order  that 
the  tightly  placed  material  may  be  benefited  by  it. 


Wallace  G.  Imhoff 

PREPARING  MATERIAL   AND   LOADING  263 

Pickling  Malleable  and  Gray  Iron  Castings 

Malleable  iron  line  material  should  be  thoroughly  washed  in  the 
lye  solution,  the  strength  of  which  must  be  about  38  pounds  of  lye 
to  each  100  gallons  of  water.  Care  must  be  taken  that  no  washed- 
off  oil  or  fat  is  allowed  to  float  in  the  tank,  and  skim  as  frequently 
as  possible.  When  the  solution  becomes  greasy  or  brownish  in 
color,  it  should  be  renewed.  If  the  tank  is  to  be  kept  busy,  the  re- 
newal should  take  place  every  other  day.  Keep  the  material  in 
the  solution  for  5  to  10  minutes,  and  drain  in  the  basket.  If  the 
material  is  covered  with  dried-out  oil,  it  should  remain  in  the  solu- 
tion for  a  longer  time. 

Wash  in  hot  water  and  drain. 

.  Place  in  the  hot  hydrofluoric  acid  solution  long  enough  until  all 
foreign  substance  has  been  removed  or  dissolved.  The  strength 
of  this  solution  should  be  about  5  per  cent.,  in  which  15  gallons 
of  30  per  cent,  commercial  hydrofluoric  acid  should  be  used  to  each 
7G.5  gallons  of  water.  The  pickling  qualities  of  this  solution  can 
be  determined  by  its  density  and  its  color.  A  hydrometer  should 
be  used  and  the  solution  should.be  about  1.026  at  15  deg.  C.,  or 
about  1.009  at  80  deg.  C.  If  the  solution  should  happen  to  be 
clear  and  its  density  less  than  the  stated  value,  acid  should  be 
added  to  maintain  its  strength.  If  the  color  of  the  solution  changes 
and  appears  brownish,  the  solution  becomes  invalid  and  should  be 
renewed.  Drain  the  material  in  this  solution. 

One  of  the  cheapest  and  most  used  methods  of  relieving  the  acid 
is  by  rinsing  in  cold  water  and  then  placing  the  material  into  a 
boiling  solution  of  cyanide  (mixture:  1  pound  of  cyanide  crystals 
to  20  gallons  of  water)  for  ten  minutes.  Material  coming  from  the 
ordinary  pickle  placed  through  this  method  will  insure  the  reliev- 
ing of  all  acid.  By  following  this  method  a  bright,  clean  coating 
of  zinc  is  assured. 

Cup-shaped  material  should  be  stacked  in  the  basket  in  such  a 
way  as  to  contain  as  little  acid  as  possible.  In  case  the  material 
should  show  defective  pickling  or  rust,  it  should  be  repickled.  In 
case  the  defects  are  slight,  sand  tumbling  can  be  applied  for  10  to 
15  minutes.  The  material  should  be  put  into  the  Sherardizing 
drum  as  soon  as  possible  after  pickling,  to  prevent  oxidation. 

Loading  the  Drums 
Alternate  layers  of  zinc  dust  and  material  should  then  be  placed 


264 


GALVANIZING  AND  TINNING 


into  the  container  within  a  few  inches  of  the  cover  to  allow  for  any 
expansion  that  may  take  place  From  3  to  5  pounds  of  zinc  dust 
should  be  used  to  each  100  pounds  of  material.  The  cover  -should 
be  made  dust  tight,  not  air  tight,  and  the  container  then  removed 
to  the  furnace. 

Fig.  129  shows  method  of  loading  a  drum  up  to  6  ft.  long.  The 
steel  loading  frame  is  placed  in  a  dusting  pan  to  catch  whatever  dust 
may  be  scattered  and  lost.  The  drum  is  placed  on  a  loading  frame 
at  an  angle  of  45  deg.  The  material  is  then  shoveled  or  placed  in 
the  drum  with  a  thorough  mixture  of  zinc,  averaging  on  bolts  and 


FIG.  129.   DRUM  ix  POSITION  FOR  LOADING 

nuts  100  pounds  of  zinc  dust  to  200  pounds  of  material.  After 
completely  filling  the  drum,  the  head  is  placed  in  position  and 
secured.  The  cover  should  fit  so  as  to  be  dust  proof,  but  HOT  air 
tight,  so  that  whatever  gases  form  within  the  drum  will  come  out 
and  burn  during  the  operation.  The  wheels  are  then  placed  on  the 
hubs  and  the  drum  placed  onto  a  transfer  car.  Care  should  be 
taken  in  seeing  that  the  horizontal  axis  of  the  drum  is  in  line 
with  that  of  the  clutch  which  revolves  it,  thereby  causing  a  true 
rotation  of  the  drum;  also  that  the  carriage  should  be  firmly  held 
within  the  furnace  by  means  of  lock  keys.  Heat  should  then  be 
applied. 

Another  method  of  loading  is  to  alternate  the  zinc  dust  and 
material  and  only  fill  to  within  6"  of  the  top. 

Fig.  130  illustrates  the  method  of  loading  from  overhead  chute. 
This  method  is  highly  recommended  in  cases  where  pipe,  tubing 
and  articles  are  Sherardized  up  to  20  ft.  long,  which  require  a  coat- 
ing on  the  inside  as  well  as  the  outside.  One  particular  item  should 


PREPARIXG  MATERIAL  AXD  LOADING 


265 


not  be  overlooked  in  the  conveying  of  the  zinc  dust  into  the  chutes 
and  hoppers.  Due  to  its  density  it  will  pack  very  close  and  a  worm 
feed  is  found  necessary  to  transfer  it  uniformly  froni  the  hopper 
into  the  drums.  The  dust  used  is  obtained  from  the  hoods  of  zinc 
smelters,  upon  which  it  is  formed  by  the  condensation  of  zinc 
vapors,  and  it  is  not  ground  commercial  zinc,  as  has  been 


FIG.  130.   LOADING  FROM:  OVERHEAD  CHUTE 

erroneously  stated.  The  dust  usually  contains  about  85  per  cent, 
pure  zinc  and  10  per  cent,  of  zinc  oxide,  which  latter  is  not  in  a 
free  state,  and,  being  evenly  distributed  throughout  the  mass,  pre- 
vents the  dust  from  becoming  pasty  at  the  high  temperature  re- 
quired for  Sherardizing. 

In  loading  flat  stock  it  is  necessary  to  have  a  layer  of  zinc  be- 
tween each  piece  of  metal,  uniformly  distributed,  and  the  drums 
should  be  rotated  the  same  as  the  cylinder  drum. 

As  zinc  dust  is  one  of  the  main  features  in  producing  good 


266  GALVANIZING  AND  TINNING 

results  in  the  process  of  Sherardizing,  special  attention  should  be 
given  this  item.  It  should  be  procured  free  from  lumps  and  with 
as  little  moisture  as  possible,  and  stored  in  galvanized  cans  and 
kept  covered  when  not  in  use. 

In  case  the  zinc  dust  is  damp  and  lumpy,  it  should  be  placed  in 
the  cylinders,  without  any  material,  drums  filled  about  one-half 
full,  and  the  cover  lightly  fastened  to  assure  relief  of  accumulating 
gases,  and  placed  in  the  furnace  at  about  350  deg.  F.  for  three 
hours.  The  zinc  dust  will  then  be  in  perfect  condition  for  use, 
after  cooling. 

The  best  results  are  obtained  when  the  zinc  dust  has  been  reduced 
to  about  50  per  cent,  metallic,  and  therefore  new  zinc  should  be 
reduced  to  that  percentage  as  rapidly  as  possible. 

Sherardized  material  shows  a  deposit  of  4  pounds  of  zinc  per 
100  pounds  of  material  treated,  as  an  average.  Therefore,  once 
it  has  been  reduced  to  the  right  percentage,  it  can  be  held  at  that 
strength  by  simply  adding  4  pounds  of  new  zinc  per  every  100 
pounds  of  material  treated.  See  that  it  is  thoroughly  mixed. 
A  chemical  analysis  once  a  week  is  recommended. 

The  above  stated  deposit  is  sufficient  to  stand  the  well-known 
Preece  test  of  four  one-minute  immersions  in  saturated  solution  of 
copper  sulphate,  U.  -S.  Government  and  Western  Electric  Co.'s  test, 
specification  No.  13110,  dated  February  3,  1908. 

Packing  the  Electric-Heated  Machine 

Material  must  be  packed  in  drum  in  such  a  way  that  no  vio- 
lent tumbling  will  occur,  else  sharp  corners  or  threaded  parts  will 
be  damaged ;  neither  should  it  be  packed  too  tight,  or  a  free  flow  of 
dust  and  heat  will  not  result  and,  consequently,  poor  Sherardizing 
will  be  obtained.  By  actual  experience  in  Sherardizing  malleable 
iron,  which  is  very  porous,  it  has  been  found  that  400  Ibs.  of  dust 
to  any  load,  ranging  from  400  Ibs.  to  1,800  Ibs.  of  material,  can 
be  used.  This  consists  of  360  Ibs.  of  used  dust  and  40  Ibs.  of 
new  Grasselli  dust.  When  small  material  is  packed  in  individual 
receptacles  to  be  placed  inside  of  Sherardizing  drum,  a  proportion 
of  about  5  Ibs.  of  dust  to  100  Ibs.  of  material  is  used.  The  dust 
should  be  mixed  in  a  tumbling  barrel  or  Sherardizing  drum  and 
sifted  through  an  80:1  mesh  riddle  before  charging  the  drum. 

Before  putting  cover  on  drum  an  asbestos  wicking  basket  is 
put  under  cover  to  make  drum  as  nearly  air  tight  as  possible. 


CHAPTER  XXVIII 

Temperature  and  Duration  of  Heats 

TEMPERATURE  and  time  are  factors  which,  depending 
upon  each  other,  are  very  important  in  the  process  of 
Sherardizing.  They  depend  on  the  choice  and  quality  of 
zinc  dust  used  and  also  on  the  requirements  and  physical  prop- 
erties of  the  Sherardized  material. 

If  common  or  blue  dust  is  used,  the  total  run  is  to  be  about  5 1/2 
hours,  of  which  about  2  hours  must  be  allowed  for  attaining  a 
maximum  furnace  temperature  of  4-10  deg.  C.  and  about  3i/2  hours 
for  a  temperature  of  440  to  450  deg.  C.  The  metallic  percentage 
of  zinc  should  be  from  35  to  45  per  cent.  The  drum  should  be 
rotated  throughout  the  whole  run  at  about  y2  r.  p.  m. 

In  case  Grasselli  dust  is  used,  the  strength  should  be  40  per 
cent,  and  upward.  The  total  run  should  be  9l/2  hours,  of  which 
2  to  2l/2  hours  must  be  allowed  for  attaining  a  maximum  furnace 
temperature  of  385  deg.  C.  and  7  to  7l/2  hours  for  a  temperature  of 
385  deg.  C.  The  container  should  be  rotated  the  same  as  for  blue 
dust. 

At  the  end  of  the  run  the  container,  if  blue  dust  is  used,  should 
be  removed  from  the  furnace  and  not  opened  until  the  temperature 
has  dropped  to  100  deg.  C.  This  will  require  8  to  24  hours,  de- 
pending upon  the  outside  temperature.  In  the  case  of  Grasselli 
dust  the  container  can  be  opened  at  a  somewhat  higher  temperature. 
No  cooling  must  be  done  by  application  of  water  or  moisture. 

Thickness  of  Coating 

Careful  attention  must  be  given  to  see  that  the  dimensions  of 
articles,  as  bolts  or  nuts,  should  be  such  as  to  allow  for  enough 
clearance  for  the  various  kinds  of  coatings.  These  dimensions, 
where  in  normal  cases  the  test  is  from  4  to  8  dips,  should  have  an 
allowance  for  a  coating  of  0.001"  to  0.002".  For  example,  if  a 
pin  for  drive  fit  is  to  be  Sherardized,  the  difference  in  diameter 
between  the  pin  and  hole  before  treatment  should  be  0.006"  to 
0.008"  if  both  surfaces  are  Sherardized. 

The  General  Electric  Co.  in  Sherardizing  their  material  deposit 
207 


GALVANIZING  AND  TINNING 


.0025"  on  a  side  or  a  total  of  .005"  on  a  diameter.  Where  threaded 
parts  are  to  be  Sherardized  they  are  undercut  or  overcut,  as  the 
case  may  be,  to  allow  for  this  deposit.  Complete  tables  of  sizes 
are  given  in  Tables  I  to  IV. 

In  case  of  Sherardized  parts  containing  holes  and  pieces  fitting 
these  holes,  the  allowance  for  Sherardizing  is  made  in  the  hole, 
in  other  words,  the  hole  is  made  .010"  larger.  This  increase  in 
deposit  is  equivalent  to  .85  to  1.1  oz.  per  square  foot. 

In  every  case  material  Sher- 
ardized as  per  above  will  stand 
170  hours  as  a  minimum  in  a 
salt  spray  without  showing  dis- 
coloration due  to  corrosion  of 
the  iron,  and  may  endure  the 
spray  even  very  much  longer. 
This  is  considered  the  most  sat- 


•» Outside  Dia 

Allowable  Variation  in  the 
Pi  tch  per  foot-?.  010" 

FIG.  131 


isfactory   and   rational   test   on 
Sherardizing.     Some  very  inter- 
esting facts  regarding  the  va- 
rious tests  are  given  in  chapter  XXXII. 

Where  body-bound  bolts  are  used  body  of  bolt  should  be  made 
to  size  and  allowance  made  in  hole  to  allow  for  Sherardizing.  Nuts 
to  be  Sherardized  should  be  tapped  .005"  larger  than  standard. 

TABLE  I 

BOLTS   AND   SCREWS    (U.    S.    STD. ) 


Size     —  

Outside  Dia.          Pitch  Dia.             Root  Dia. 

Min. 

Max. 

Dif. 

Min. 

Max. 

Dif. 

Min. 

Max. 

Dif. 

%"  -20 

.245 

725(T 

.005 

.21  sF 

.2176 

.0025 

.1801 

.1851 

.005 

%eM8 

.3075 

.3125 

.005 

.2740 

.2765 

.0025 

.2353 

.2403 

.005 

%"  -16 

.370 

.375 

.005 

.3319 

.3344 

.0025 

.2888 

.2938 

.005 

7/i6"-14 

.4325 

.4375 

.005 

.3886 

.3911 

.0025 

.3397 

.3447 

.005 

&"  -13 

.495 

.500 

.005 

.4476 

.4501 

.0025 

.3951 

.4001 

.005 

o/16"-12 

.5565 

.5625 

.006 

.5054 

.5084 

.003 

.4481 

.4541 

.006 

%"  -11 

.619 

.625 

.006 

.5630 

.5660 

.003 

.5009 

.5069 

.006 

%"  -10 

.744 

.750 

.006 

.6821 

.6851 

.003 

.6141 

.6201 

.006 

%"  -  9 

.869 

.875 

.006 

.7999 

.8029 

.003 

.7247 

.7307 

.006 

1"   -  8 

.994 

.000 

.006 

.9158 

.9188 

.003 

.8316 

.8376 

.006 

1%"  -  7 

.117 

.125 

.008 

.0282 

.0322 

.004 

.9314 

.9394 

.008 

Hi"  -  7 

242 

.250 

.008 

.1532 

.1572 

.004 

1.0564 

.0644 

.008 

1%"  -  6 

.367 

.375 

.008 

.2628 

.2668 

.004 

1.1505 

.1585 

.008 

1*1"  -  6 

.492 

1.500 

.008 

.3878 

.3918 

.004 

1.2755 

.2835 

.008 

l-'/s"  -  % 

.017 

.625 

.008 

.5029 

.5069 

.004 

1.3808 

.3888 

.008 

i%"  -  r, 

.742 

.750 

.008 

.6161 

.6201 

.004 

1.4822 

.4902 

.008 

1%"  -  5 

.867 

.875 

.008 

.7411 

.7451 

.004 

1.6072 

.6152 

.008 

2"   -  41^ 

.992 

2.000 

.008, 

.8517 

1.8557 

.004 

1.7033 

.7113 

.008 

TEMPERATURE  AND  DURATION  OF  HEAT 


TABLE  II— SHERARDIZED 


BOLTS  AND  SCREWS 

DIMENSIONS 

BEFORE  SHERARDIZING 

Outside  Dia. 
Size 

Pitch  Dia.            Root  Dia. 

Min. 

Max. 

Dif. 

Min. 

Max. 

Dif. 

Min. 

Max. 

Dif. 

H"  -20 

.2400 

.2450 

.005 

.2101 

.2126 

.0025 

.1751 

.1801 

.005 

r/16"-l8 

.3025 

.3075 

.005 

.2690 

.2715 

.0025 

.2303 

.2353 

.005 

%"  -16 

.3650 

.3700 

.005 

.3269 

.3294 

.0025 

.2838 

.2888 

.005 

7/16"-14 

.4275 

.432->  .00.-) 

.3836 

.3861 

.0025 

.3347 

.3397 

.005 

1.2"  -13 

.4900 

.4950  .005 

.4426 

.4451 

.0025 

.3901 

.3351 

.005 

y16"-12 

.5515 

.5575 

.006 

.5004 

.5034  |  .0030 

.4431 

.4491 

.006 

%"  -11 

.6140 

.620 

.006 

.5180 

.5610 

.0030 

.4959 

.5019 

.006 

%"  -10 

.739 

.745 

.006 

.6771   .6801 

.0030 

.6091 

.6151 

006 

%"  -  9 

.864 

.870 

.006|  .7949   .7979 

.0030 

.7197 

.7257 

.006 

1"   -  8 

.980 

.905 

.006 

.9108   .9138  .0030 

.8266 

.8326 

.006 

1%"  -  7 

1.112 

1.120 

.008 

1.0232  1.0272  .0040 

.9264 

.9344 

.008 

1%"  -  7 

1.237 

1.24) 

.008 

.14S2  1  .  1V22  i  .0040 

.0514 

1.0594 

.008 

1%"  -  6 

1.362 

1.370 

.008 

.•257S  1.261S 

.0040 

.1455 

1.1535 

.008 

1%"  -  6 

1.487 

1.495 

.008 

.3828  1.:J86S 

.0040 

.2705 

1.2785 

.008 

1%"  -  5& 

1.612 

1.620 

.008 

.4979  1  ..-;(>  19 

.0040 

.3758 

1.3838 

.008 

1%"  -  5 

1.737 

1.745 

.008 

.6111 

1.6151 

.0040 

1.4772 

1.4852 

.008 

1%"  -  5 

1.862 

1.870 

.008 

.7361 

1.7401 

.0040 

.6022 

1.6102  .008 

2"   -  41^ 

1.987 

1.995 

.008 

.S4f,7  1.S-.07  .00-10   .6983 

1.7063  1  .008 

TABLE  TIT 

MACHINE  SCREWS  (A.S.M.E.  STD.  ) 

Outsida  Dia. 


Root  Dia. 


Min. 

Max. 

Diff. 

Min. 

Max. 

Diff. 

Min. 

Max. 

Diff. 

0-80 

.0572 

.060 

.002S 

.0~,05 

.0519 

.0014 

.0410 

.0438 

.0028 

1-72 

.0700 

.073 

.0030 

.0625 

.0640 

.0015 

.0520 

.0550 

.0030 

2-64 

.0828 

.086 

.0032 

.0743 

.0759 

.0016 

.0624 

.0657 

.0033 

3-56 

.0955 

.099 

.0035 

.0857 

.0874 

.0017 

.0721 

.0758 

.0037 

4-48 

.1082 

.112 

.0038 

.0966 

.0985 

.0019 

.0807 

.0849 

.0042 

5-44 

.1210 

.12-) 

.0040 

.1082 

.1102 

.0020 

.0910 

.0955 

.0045 

6-40 

.1338 

.138 

.0042 

.1197 

.1218 

.0021 

.1007 

.1055 

.0048 

8-36 

.1596 

.164 

.0044 

.1438 

.1460 

.0022 

.1227 

.1279 

.0052 

10-30 

.1852 

.190 

.0048 

.1660 

.1684 

.0024 

.1407 

.1467 

.0060 

12-28 

.2111 

.216 

.0049 

.1904 

.1928 

.0024 

.1633 

.1696 

.0(163 

14-24 

.2368 

.242 

.0052 

.2123 

.2149 

.,0026 

.1808 

.1879 

.0071 

TABLE  IV— SHERARDIZED 

MACHINE    SCREWS 


DIMENSIONS    BEFORE    SHEKARDIZING 


Outside  Dia. 


Pitch    Di 


Min. 

Max. 

Diff. 

Min. 

M». 

Diff. 

Min. 

Max. 

Diff. 

6-40 

.1288 

.133 

.0042 

.1147 

.1168 

.0021 

.0957 

.1005 

.0048 

8-36 

.1546 

.159 

.0044 

.1388 

.1410 

.0022 

.1177 

.1229 

.0052 

10-30 

.1802 

.185 

.0048 

.1(510   .1634   .0(124   .1357 

.1417 

.0060 

12-28 

.2061 

.211 

.0049 

.is:>t   .1S7S   .0024   .1583 

.1846 

.0063 

14-24 

.2318 

.2:57 

.0052 

.2i>7-'!   .2.  )'.»!!   .0026   .17")S 

.1829 

.0071 

270 


GALVANIZING  AND  TINNING 


When  the  article  Sherardized  will  be  subjected  to  sharp  bending 
or  to  considerable  variations  of  temperature,  the  thickness  of  coat- 
ing will  be  limited,  for  zinc,  being  more  brittle  and  having  a  dif- 
ferent coefficient  of  expansion  than  iron,  will  separate  from  the 
iron  under  these  extreme  conditions  if  too  thick  a  coating  is  applied. 

Temperature  an  Important  Factor 

As  mentioned  before,  the  effect  of  temperature  is  an  important 
factor  in  both  elements  of  the  process,  as  the  iron,  with  the  increase 
of  temperature,  increases  its  power  of  absorption  of  zinc  vapor  and 
likewise  the  vapor  tension  of  zinc  increases  with  the  temperature. 
According  to  authorities  on  vapor  tension,  with  an  increase  of 


JUUU 

00* 

1 

•004 
.003 
.002 

.001 

0 
2L 

1 

/ 

I 

/ 

/ 

/I 

/ 

^ 

„_ 

— 

— 

—  •""" 

X)     Z4O     280      320      360     400     44O     48 

Degrees  C. 

CHART  I.    RATE  OF  DEPOSIT  AND  TEMPERATURE  IN  ELECTRIC  HEATED 
SHERARDIZING  MACHINE 

temperature  from  325  to  375  dog.  C.,  the  relative  vapor  tension 
increases  14  times,  and  from  825  to  425  deg.  C.,  the  relative  vapor 
tension  increases  1)2  times.  The  absorption  of  zinc  vapors  by  vari- 
ous metals  (copper,  nickel  and  iron)  approaches  the  same  rate  at 
high  temperatures  up  to  about  the  melting  point  of  zinc.  Above 
this  the  absorption  is  exceedingly  rapid. 

From  curves  obtained  by  A.  R.  Johnson  and  W.  R.  Woolrich,  it 
is  seen  that  the  greatest  variation  of  absorption  Avith  a  variation  of 
temperature  lies  near  the  melting  point  of  zinc,  thus  a  fluctuation 
of  lower  temperature  does  not  affect  the  absorption  of  the  zinc 


TEMPERATURE  AND  DURATION  OF  HEAT 


271 


vapor  to  the  same  extent  as  at  higher  temperatures.  In  other 
words,  more  uniform  absorption  of  zinc  vapor  is  obtained  at  lower 
temperatures. 

In  view  of  the  above  facts  it  appears  that  when  a  metal  is  heated 
in  the  presence  of  the  vapor  of  another  metal,  or  the  vapor  of  other 
elements  or  compounds,  the  metal  evolves  a  portion  of  the  gases  or 
vapor  which  it  contains,  and  in  exchange  accommodates  the  precipi- 
tation of  the  other  vapors  within  its  pores. 

Operation  of  the  Electric  Heated  Drum 
The  drum  is  started  revolving  at  about  f  to  1  r.p.m.  and  switch 
thrown  to  "high  heat."    The  high  heat  is  used  to  bring  drum  up 
to  desired  temperature  (350  deg.  to  375  deg.  C.)  to  give  correct 


600 


400 


'300 


ZOO 


100 


50 


10 


20 


01     2    3    4    5    6     7    8    9    10    II    12   13   14   15  16    17 
Hours  Run 

CHART  II.    TEMPERATURE  AND  POWER  CURVE  OF  ELECTRIC-HEATED  SHER- 
ARDIZING  MACHINE  24"  x  24"  x  40" 

deposit,  and  then  the  low  heat  is  thrown  on  to  hold  it  at  that  tem- 
perature for  the  required  period  (2^  to  3  hours)  to  give  the  de- 
posit. After  this  current  is  thrown  off  and  drum  allowed  to  cool 
to  180  deg.  C.,  which  is  a  safe  temperature  to  open  drum.  This 
should  apply  to  Grasselli  zinc  only,  as  blue  dust  will  fuse  more 


272  GALVANIZING  AND  TINNING 

rapidly.    Charts  I  and  II  provide  interesting  records  of  the  power, 
temperature  and  deposit. 

Sherardizing  with  Zinc  Under  Vacuum 

After  reading  the  above  it  is  clear  that  to  do  Sherardizing  we 
should  have  the  zinc  vapors  at  their  greatest  tension  and  have  Sher- 
ardized  iron  in  condition  to  give  oif  the  maximum  gases.  Zinc  boils 
under  ordinary  pressure  at  913  deg.  C.,  and  the  boiling  point  under 
vacuum  is  reduced  to  548  deg.  C.  Iron  on  being  heated  from  500 
to  600  deg.  C.  in  vacuum  gives  off  gases  readily.  Therefore,  it  is 
quite  clear  that  in  vacuum  the  conditions  are  best  for  Sherardizing, 
and  the  writer  was  able  to  produce  condensation  of  zinc  on  iron 
in  a  very  short  time.  Some  of  the  results  were  obtained  under  these 
conditions  in  minutes,  where  with  ordinary  pressure  under  the  same 
conditions  it  required  hours.  This  process  and  the  machine  for 
treating  material  by  this  method  have  been  covered  by  patents. 

The  process  is  not  necessarily  dependent  on  having  the  substances 
supplying  the  vapor  in  the  form  of  a  powder,  although  a  substance 
in  this  form  may  often  be  raised  to  a  temperature  above  the  melting 
point  without  fusing  the  articles  together.  The  elevated  tempera- 
ture which  can  thus  be  secured  is  of  material  assistance  in  securing 
a  rich  vapor,  which  naturally  hastens  the  process  and  therefore  is 
an  advantage  in  many  cases.  A  further  advantage  of  using  the 
material  supplying  the  vapor  in  the  powdered  form  is  the  enor- 
mously increased  surface  which  can  thus  be  secured,  thus  giving  a 
richer  vapor,  since  the  amount  of  material  vaporized  at  a  given 
temperature  and  pressure  increases  with  increased  evaporating  sur- 
face. This  is  particularly  of  value  when  the  boiling  point  of  the 
vapor-giving  material  is  above  the  temperature  at  which  the  deposi- 
tion occurs. 

Time  an  Important  Factor 

Just  as  temperature,  so  time  is  an  important  factor  in  the  process 
of  Sherardizing.  Since  articles  of  different  size,  shape  and  char- 
acter are  treated,  if  each  were  given  its  ideal  condition  of  tempera- 
ture and  quality  of  zinc  dust,  the  time  of  treatment  of  all  would  be 
alike,  but  this  is  not  practical,  for  it  is  easier  to  vary  the  time  of  the 
process  than  the  other  factors. 

It  is  possible  to  obtain  almost  instantaneous  Sherardizing  in  the 
case  of  wire  heated  to  a  high  temperature  and  allowed  to  pass 


TEMPERATURE  AND  DURATION  OF  HEAT  273 

through  zinc  dust  at  normal  temperature.  In  the  case  of  many 
articles  to  be  Sherardized  this  method  is  impractical  and  so  longer 
periods  of  time  are  required.  Not  only  the  time  of  heating  the 
article  during  the  process  should  be  considered  but  also  the  time  of 
cooling,  for  this  process  is  not  confined  to  any  one  particular  tem- 
perature, but  takes  place  over  a  wide  range  of  temperature.  If  the 
articles  being  treated  have  not  become  saturated  during  the  heating 
period,  the  process  will  still  continue  upon  cooling,  until  the  tem- 
perature falls  below  its  minimum  point.  There  are  two  reasons  for 
slowly  cooling :  First,  to  prevent  loss  from  exposing  hot  zinc  dust 
to  the  atmosphere  (the  metallic  zinc  particles  would  quickly  oxi- 
dize) ;  second,  to  prevent  the  articles  being  chilled  too  quickly. 

Motion  During  Sherardizing 

The  general  public  has  been  given  to  understand  that  this  is  a 
tumbling  process,  and  that  the  zinc  will  not  deposit  unless  the 
drums  are  continuously  rotating.  If  the  articles  are  thoroughly 
mixed  with  the  dust,  it  is  not  necessary  to  have  the  drums  continu- 
ously rotating  to  insure  uniform  deposit,  providing  that  the  drums 
are  not  over  20  in.  in  diameter.  An  occasional  turn  of  once  in  15 
minutes  is  ample  to  insure  good  results;  too  much  rotating  under 
heat  pressure  will  make  the  articles  appear  dark  and  dusty. 

Sherardizing  can  be  and  is  being  done  where  the  articles  to  be 
treated  are  placed  in  the  zinc  dust,  heat  applied,  but  no  motion 
given  to  either  the  dust  or  the  articles  during  the  process.  This 
method  is  used  in  the  case  where  large  pieces,  plates  and  sheets  are 
being  treated.  If  the  transmission  of  heat  through  zinc  dust  were 
perfect  and  if  the  deterioration  of  the  zinc  particles  were  negligible, 
the  motion  of  the  articles  during  treatment  would  be  unnecessary. 
Such,  however,  is  not  the  case,  for  zinc  dust  is  a  poor  conductor  of 
boat  and  the  deterioration  of  the  zinc  particles  in  intimate  contact 
with  the  article  treated  requires  a  replacement  of  the  same  by  new 
particles.  Since  this  process  continues  during  the  cooling  period, 
until  it  reaches  its  critical  point,  where  it  ceases,  the  motion  will 
produce  the  same  effect  then  as  during  the  heating  period. 

Zinc  dust,  which  is  commonly  called  blue  powder,  is  a  flue  dust 
and  therefore  a  by-product  of  the  zinc  smelting  furnace  known  as 
the  Belgian  furnace.  It  contains,  as  a  rule,  from  75  per  cent,  to 
90  per  cent,  pure  zinc.  The  supply  is  ample  at  a  price  a  fraction 
above  that  of  spelter,  and  it  can  be  procured  in  any  quantities  that 


274  GALVANIZING  AND  TINNING 

may  be  required.  The  nature  of  the  zinc,  which  is  given  off  at  a 
temperature  of  1,000  deg.  C.  or  more  at  the  inception  of  distilla- 
tion, comes  into  contact  with  the  comparatively  cold  atmosphere  of 
the  flue  and  the  sudden  chill  causes  a  rapid  condensation  of  the 
vapor,  so  rapid,  indeed,  that  it  skips  the  liquid  state  and  drops  into 
the  shape  of  perfectly  spherical  articles,  of  which  about  30,000,000 
can  be  crowded  into  a  cube  measuring  1/16"  in  every  direction. 
This  impalpable  powder,  notwithstanding  its  high  specific  gravity, 
for  it  is  only  about  10  per  cent,  lighter  than  pure  zinc,  can  be 
blown  about  like  lyeopodium.  It  is  used  very  extensively  by  textile 
manufacturers  for  dye  work,  and  by  paint  manufacturers,  and  is 
sold  packed  in  barrels  holding  about.  1,500  pounds.  It  cannot  be 
melted  into  slabs  on  account  of  its  rapid  oxidation  at  a  very  low 
temperature.  The  peculiar  properties  of  zinc  dust  have  been 
ascribed  by  some  to  the  presence  of  cadium  which,  being  of  more 
volatile  metal,  is  distilled  first  from  ore  and  then  condensed  into 
flues.  One  observer  finds  quantities  ranging  from  0.283  to  0.794 
per  cent,  in  flue  dust  after  two  hours  of  furnace  operation.  Others 
have  claimed  that  these  properties  are  due  to  the  presence  of  zinc 
oxide  or  other  impurities.  Most  of  the  zinc  is  purchased  in  Belgium 
or  Silesia.  Silesian  zinc  has  been  found  the  best  adapted  for  Sher- 
ardizing, due  to  the  fact  that  it  has  less  moisture.  A  sample  of  an 
analysis  showed  the  following: 

Metallic  zinc 88.95%       Cadium   0.62% 

Zinc  oxide 6.88%       Sulphur   0.055% 

Lead 3.45%       Iron   0.04% 

A  fact  that  is  undoubtedly  responsible  in  a  great  measure  for  the 
mystery  attaching  to  the  action  of  zinc  dust  is  its  readiness  to 
oxidize.  It  is  only  when  oxidation  is  put  out  of  its  power,  as  in 
the  closed  Sherardizing  drum,  that  heat  will  produce  sufficient  over- 
strain to  cause  the  particle  to  burst  into  vaporized  gas.  This  gas, 
so  suddenly  released,  will  condense  instantly  on  the  coolest  spaces 
it  can  find.  In  Sherardizing,-  the  coolest  spaces  are  on  the  articles 
in  the  drum. 

It  is  an  established  fact  that  in  Sherardizing  the  presence  of 
zinc  oxide  is  necessary.  We  might  suppose,  therefore,  that  a  mole- 
cule of  oxide  is  reduced  to  voltaic  action  when  it  comes  into  con- 
tact with  the  iron.  The  zinc  attaches  itself  to  the  iron,  which  acts, 
therefore,  as  a  cathode  in  electrolysis,  and  the  oxygen  travels  in  the 


TEMPERATURE  A^TD  DURATION  OF  HEAT  275 

opposite  direction,  combines  with  a  free  molecule  of  zinc  to  form 
a  molecule  of  oxide,  and  goes  through  the  same  performance  as 
before. 

Zinc  dust  appears  to  break  down  into  vapor  at  about  150  to  200 
deg.  C.,  although  it  undoubtedly  begins  to  disintegrate  at  a 
lower  heat.  As  the  pressure  increases  it  takes  a  greater  amount  of 
heat  to  cause  the  breakdown.  As  the  vapor  condenses  the  pressure 
is  relieved  and  the  hotter  articles  of  dust  are  vaporized  and  re- 
establish an  equilibrium. 

Being  a  gas,  the  zinc  vapor  can  force  itself  into  the  pores  of  the 
metal  and  form  a  deposit  to  a  depth  which  will  increase  with  the 
duration  of  the  treatment. 

Eapid  cooling  will  cause  the  zinc  to  condense  as  crystals,  the  ad- 
herence of  which  to  the  iron  is,  however,  inversely  proportional 
to  their  size.  Normal  cooling  would  seem  to  yield  in  all  cases  a 
fine,  glossy  surface  of  what  can  be  appropriately  termed  ferrozinc. 

General  Operation 

There  are  three  factors  to  contend  with  in  the  process  of  Sher- 
ardizing,  viz.,  zinc  dust,  temperature,  and  the  length  of  time  the 
heat  is  run. 

For  example,  take  a  standard  size  cylinder  or  drum  15"  to  20" 
in  diameter,  14"  wall,  new  zinc  dust  at  90  per  cent,  metallic,  tem- 
perature 750  deg.  to  950  deg.  F.  outside  of  drum,  with  pyrometer 
stem  showing  at  the  bottom  of  the  drums  and  protected  from  the 
flame  by  a  baffle  plate,  the  furnace  started  cold  and  allowing  two 
hours  to  bring  the  temperature  up  to  the  required  number  of 
degrees  and  held  at  that  point  for  three  hours,  should  give  good 
results.  If,  however,  the  deposit  should  not  be  sufficient,  then  the 
temperature  should  be  slightly  increased,  say  25  deg.  or  the 
time  of  operation  extended;  but  rules  generally  followed  to 
compare  with  the  ordinary  ten  hour  per  day  time  is  to  increase  the 
temperature,  which  applies  to  ordinary  material  only.  In  cases 
where  high  tempered  steel  or  spring  stock  is  treated  the  time  of 
operation  should  be  extended  and  the  temperature  reduced  to  about 
650  deg.  F.  for  a  15"  drum  and  700  deg.  F.  for  a  20"  drum.  The 
drums  are  then  taken  out  and  allowed  to  cool  (under  no  circum- 
stances should  the  drums  be  opened  while  hot,  as  the  zinc  dust  will 
fuse  and  burn). 

The  time  generally  allowed  for  heats  on  ordinary  material  is 


276 


GALVANIZING  AND  TINNING 


five  and  a  half  hours  for  the  first  heat,  started  from  a  cold  furnace, 
and  four  and  a  half  hours  for  the  second  heat,  which  allows  one- 
half  hour  for  making  the  change. 


FIG.  132.   UNLOADING  INTO  ROTARY  DUST  SEPARATOR 

After  loading,  the  drums  are  scaled  and  rolled  into  the  Sher- 
ardizing  furnace,  as  shown  in  Fig.  119  or  128.  Here  they  remain 
for  5  to  6  hours,  according  to  the  tonnage  that  they  contain,  in  an 
evenly  maintained  temperature  of  780  deg.  F. 

Cooling  and  Unloading 

Upon  removal  from  the  Sherardizing  furnace  the  drums  are 
rolled  out  on  the  cooling  platform,  as  shown  in  Fig.  120  or  128, 
and  allowed  to  cool  out,  as  it  is  called,  for  12  to  16  hours  before 


TEMPERATURE  AND  DURATION  OF  HEAT  27? 

they  are  unsealed,  as  the  introduction  of  oxygen  to  the  zinc  while  in 
a  superheated  state  would,  of  course,  destroy  it.  The  annealing  in- 
cident to  the  slow  heating  and  slower  cooling  through  which  articles 
pass  in  the  process  makes  Sherardizing  doubly  valuable  as  a  finish 
for  steel  products  which,  like  electrical  conduits,  must  be  bent 
during  installation,  and  for  many  cast-iron  articles  which  would 
otherwise  require  a  separate  operation  for  the  purpose. 

After  "cooling  out"  the  contents  of  the  drums  are  dumped  into 
large  hoppers,  as  shoAvn  in  Fig.  132,  and  the  surplus  zinc  dust 
rocked  out,  leaving,  in  addition  to  the  zinc-iron  alloy,  an  exterior 
coatinsr  of  zinc. 


CHAPTER  XXIX 

Don'ts  in  Sherardizing  Practice 

THE  following  account  of  the  inspection  and  reorganization 
of  a  Sherardizing  plant  is  included  so  the  users  of  this  book 
may  profit  by  the  experience  of  others  and  use  the  many 
valuable  suggestions  it  contains  in  their  own  practice. 

The  plant  was  installed  for  the  purpose  of  Sherardizing  ma- 
terial for  their  own  product.  The  material  included  bolts,  nuts, 
malleable  iron  castings  and  line  material.  When  the  plant  was  in- 
stalled the  men  in  charge  of  the  plant  knew  practically  nothing 
about  the  process.  Sherardizing  was  clone  in  the  same  room  with 
pickling  and  hot  galvanizing.  .  The  steam  and  acid  fumes  from  the 
large  pickling  tanks  (used  for  pickling  large  castings  preparatory 
to  painting)  not  only  had  a  deleterious  effect  upon  the  Sherardiz- 
ing process,  but  also  in  connection  with  the  zinc  dust  in  the  air, 
made  working  conditions  almost  intolerable.  Whenever  articles 
were  pickled  in  large  quantities  they  were  first  placed  in  an  empty 
acid  tank  and  the  acid  and  water  poured  over  them  until  covered. 
When,  on  inspection,  the  pickling  process  was  completed,  the  acid 
was  allowed  to  run  into  the  sewer.  Before  all  of  these  pickled 
articles  could  be  washed  off  most  of  them  had  acquired  a  thin 
coating  of  rust  which  necessitated  another  dip  in  the  acid  before 
being  Sherardized.  No  unloading  pit  had  been  provided,  the  dust 
being  dumped  upon  the  floor  to  be  trampled  under  foot  and,  on  sev- 
eral occasions,  to  be  flooded  by  water.  The  ovens,  too,  were  not 
suitable  for  the  work.  The  clutches  which  connected  the  drums 
with  the  driving  mechanism  were  crude  and  clumsy  so  that  they 
could  not  be  applied  from  outside.  This  necessitated  cooling  of 
the  ovens  to  allow  a  workman  to  enter  the  oven  to  attach  a  clutch. 

Considerable  trouble  had  been  encountered  by  the  dust  caking 
and  balling  in  the  drums.  This  became  so  bad  at  times  that  nearly 
a  whole  drum  of  work  would  be  scrapped  and  much  dust  wasted. 
This  condition  was  practically  eliminated  by  confining  the  dust 
in  a  bin  away  from  all  water  or  acid  vapors,  as  well  a&  keeping  the 
temperature  within  the  limits  for  the  particular  dust  used.  The 
large  pickling  tanks  and  paint  tank  were  removed  from  the  build- 

278 


* 
DON'TS  IN  SHERARDIZING  PRACTICE  27& 

ing,  giving  more  room,  improving  working  conditions  considerably 
and  especially  reducing  the  amount  of  acid  fumes  coming  in  con- 
tact with  the  zinc  dust. 

Eliminating  Black  Spots  on  Finished  Work 

One  of  the  principal  difficulties  was  the  elimination  of  black 
spots  on  the  finished  work.  At  times  this  became  very  excessive, 
not  only  detracting  from  the  appearance  of  the  work  but  also  re- 
ducing the  number  of  dips  the  material  would  stand  under  test. 
Two  principal  causes  were  found  for  this  fault.  The  first  was  the 
presence  of  "burnt  in"  slag  in  the  corners  or  crevices  of  the  ma- 
terial which  it  was  almost  impossible  to  remove  by  pickling  in  some 
instances.  This  was  corrected  by  more  intelligent  inspection  of 
the  material,  both  before  and  after  pickling.  In  connection  with 
inspection,  it  was  found  that  the  material  received  practically  no 
inspection  before  treatment.  Whenever  slaggy  material  reached 
the  Sherardizing  department,  the  inspector  was  notified  and  it  was 
often  found  that  the  material  had  been  removed  from  the  foundry 
more  than  two  years  before.  An  entirely  new  system  of  inspection 
has  since  been  adopted,  which  has  taken  care  of  the  black  spots 
from  this  cause. 

The  second  cause  was  the  presence  of  acid  in  the  spongy  or  por- 
ous parts  of  a  casting  which  was  not  thoroughly  washed  out  or 
neutralized.  It  was  difficult  to  obtain  castings  without  some  por- 
ous parts  or  corners  that  were  filled  Avith  fine  cracks,  but  by  careful 
attention  to  pickling  and  neutralizing  the  black  spots  were  re- 
duced to  a  minimum. 

Obviating  Non-Uniformity  of  Coating 

Another  fault  was  the  non-uniformity  of  coating  even  with  the 
same  kind  of  material  in  the  same  drum  as  shown  by  testing  some 
of  the  material  from  different  parts  of  the  drum.  A  heat  analysis 
of  the  furnaces  showed  a  variation  of  temperature.  This  affected 
the  uniformity  of  coating  considerably,  notwithstanding  the  drums 
were  rotated  through  the  run.  This  fault  was  corrected  by  putting 
new  baffles  in  the  furnace,  additional  heat  insulation  on  the"  doors, 
and  new  burners,  which  gave  more  uniform  distribution  of  heat. 
New  clutches  were  also  included  in  the  general  overhauling  of  the 
furnaces,  which  allowed  the  driving  mechanism  to  be  connected  to 
the  drums  from  outside  the  furnaces. 


280  GALVANIZING  AND  TINNING 

In  order  to  save  the  excessive  waste  of  acid  eight  small  pickling 
tanks  were  installed,  together  with  sufficient  baskets  for  handling 
the  material.  An  electric  hoist  was  installed  for  handling  the 
baskets  of  material  from  one  tank  to  another.  By  this  betterment 
the  quality  of  pickling  was  improved  as  well  as  reducing  the  amount 
of  supervision  required  because  of  systematizing  the  process.  By 
handling  the  material  in  smaller  quantities  during  pickling  it  was 
found  that  better  inspection  was  possible. 

Some  difficulty  was  encountered  in  the  case  of  one  particular 
malleable  iron  article,  or  cap,  which  was  swedged  on  the  end  of  a 
wooden  rod.  In  this  case  the  Sherardizing  must  be  done  before 
the  iron  cap  was  formed  on  the  rod.  Whenever  the  Sherardizing 
was  heavy  this  forming  process  would  cause  the  cracking  or  peeling 
of  the  coating.  By  increasing  the  temperature  and  decreasing  the 
time  of  the  process  (using  blue  dust)  the  quality  of  the  coating 
was  much  improved.  In  this  way  the  Sherardized  articles  would 
stand  the  same  number  of  dips  test  with  a  much  thinner  coating 
and  would  retain  their  coating  through  the  forming  process. 

Improving  Psychological  Condition  of  Men 

In  this  connection  the  improvement  in  the  psychological  condi- 
tion of  the  men  cannot  be  overlooked.  Under  the  adverse  condi- 
tions the  men,  including  those  in  charge,  were  very  skeptical  of  the 
process.  By  explaining  the  process  to  them  and  investigating  each 
part  of  the  process  with  their  co-operation  it  was  found  that  much 
could  be  accomplished.  This  was  done  by  improving  the  unbear- 
able working  conditions,  as  well  as  those  having  a  direct  bearing 
upon  the  process.  Since  these  improvements  were  made  this  plant 
has  been  doing  as  good  work  as  any  others,  while  still  further  im- 
provements would  probably  increase  the  convenience  and  lessen  the 
cost  of  the  process.  This  is  an  example  of  what  has  been  done  in 
•one  case  to  improve  a  plant  and  may  be  a  means  of  helping  others 
to  overcome  their  difficulties,  who  have  had  the  same  or  similar 
conditions  to  contend  with. 

It  must  be  understood  that  zinc  penetrating  the  metal  is  bound 
to  bring  to  the  surface  all  impurities  and,  while  it  does  not  inter- 
fere with  the  rust  proofing  qualities  of  the  article,  it  makes  it 
objectionable  in  appearance.  The  claim  has  been  made  that  articles 
coming  direct  from  the  machine,  covered  with  oil,  can  be  Sherard- 
ized without  cleaning.  This  is  true  where  no  fats  are  used  with  the 


DON'TS  IN  SHERARDIZING  PRACTICE  281 

oil.  In  case  of  fats  where  the  zinc  will  absorh  it,  it  will  redeposit 
these  fats  on  the  surface  in  the  form  of  oxides,  which  has  been  mis- 
taken in  some  instances  for  rust,  as  the  appearances  are  very  nearly 
alike.  The  two  main  fats  used  in  oil  for  cutting  down  threads 
are  bean  oil  and  cotton  seed  oil.  In  case  of  clean  oil,  free  from 
fats,  with  the  zinc  of  sufficient  strength  to  force  its  way  through 
and  absorb  the  oil,  no  special  cleaning  is  required,  but  experiment- 
ing along  these  lines  brings  out  the  work  dark.  This  also  is  an 
objectionable  feature  and  therefore  has  not  been  found  practicable 
when  considering  the  small  cost  of  cleaning. 

Caution 

Careful  attention  must  be  given  to  see  that  the  dimensions  of 
the  bolts  and  nuts  shall  be  such  as  to  allow  for  enough  clearance 
for  the  various  kinds  of  zinc  coating.  These  dimensions,  where  in 
normal  cases  the  test  is  from  G  to  8  dips,  should  have  an  allowance 
for  8  to  9  mils. 

Don'ts 

DON'T  deposit  0  or  8  pounds  of  zinc  to  make  the  article  rust 
proof.  Four  pounds  is  sufficient,  as  too  heavy  a  deposit  will  render 
the  coating  brittle  and  it  will  flake. 

DON'T  take  it  for  granted  that  just  because  you  have  a  nice, 
bright  color  it  is  rust  proof.  Test  it  and  find  out,  as  colors  are 
very  deceiving. 

DON'T  mix  your  floor  sweepings  in  with  your  zi'nc.  Save  it  and 
sell  it,  as  the  zinc  dust  in  continuous  contact  with  iron  will  gather 
dirt  quickly  enough. 

DON'T  leave  sawdust  and  excelsior  on  the  work  to  mix  with  the 
zinc  as  it  will  oxidize  and  darken  the  zinc  and  the  material. 

DON'T  let  your  zinc  dust  stand  around  in  open  boxes  or  barrels 
as  it  will  absorb  moisture.  Keep  it  in  galvanized  cans  and  covered. 

DON'T  throw  water  on  zinc  in  case  of  fire  as  same  will  produce 
gas.  Smother  it  with  a  blanket  or  sand. 

DON'T  get  scared  if  you  should  look  into  the  furnace  and  see 
fire  around  the  cracks  of  your  drums.  It  will  stop  as  soon  as  the 
gas  obtained  from  the  moisture  is  burnt  out. 

DON'T  open  the  drums  until  they  are  cold,  or  at  least  150  deg.  F. 

DON'T  expect  Sherardizing  to  fill  an  uncalked  seam.  It  is 
not  a  solder. 


CHAPTER  XXX 

Coloring  and  Finishing  Sherardized  Articles 

BY  BUFFING  the  surface  on  a  fine  polishing  wheel  and 
afterwards  placing  it  on  a  cloth  wheel  for  color,  a  finish 
can  be  obtained  which  is  more  brilliant  than  nickel 
plating,  comparing  very  favorably  with  silver  plating,  and 
which  will  not  tarnish.  The  article  Sherardized  is  a  frac- 
tion darker  and  more  velvety  in  appearance,  due  to  the  zinc 
coating,  where  nickel  is  a  white  coating.  When  cutting  down 
for  this  finish  the  impression  generally  carried  is  that  all  the 
zinc  is  being  ground  off  and  relieved  from  the  surface.  This  is  not 
the  case,  due  to  zinc  alloy,  and  if  closely  inspected  a  fine  zinc  coat- 
ing will  show,  even  through  the  most  brilliant  finish,  and  there  is 
perfect  rust  protection,  so  long  as  this  veining  is  visible  to  the 
naked  eye.  Further,  the  friction  from  a  wheel  caused  in  burnish- 
ing up  the  surface  has  a  tendency  to  increase  the  crystal  hardness 
of  this  coating  so  that  it  further  resists  weather  action. 

By  taking  a  piece  of  cold  rolled  steel  and  Sherardizing  it  to  a 
thickness  of  .GOl1/*/',  and  passing  it  through  the  rolls  cold  and 
breaking  it  down  twice  its  length,  it  will  still  show  the  same  resist- 
ance against  copper  sulphate  tests  as  before  this  reduction  was 
made.  This  goes  to  prove  that  the  more  friction  that  is  brought  to 
bear,  as  previously  stated,  the  more  resistance  against  corrosion.  It 
has  also  been  found  that  material  can  be  top  finished  in  nickel, 
brass,  copper  and  bronze,  also  can  be  readily  japanned,  enameled, 
and  painted. 

In  the  case  of  copper  and  bronze,  after  plating,  the  material 
should  be  set  aside  and  let  stand  for  forty-eight  to  seventy-two 
hours,  for  action  between  zinc  and  copper  or  bronze.  This  action 
makes  the  surface  appear  very  dark  but,  after  this  action  ceases, 
the  work  is  then  placed  on  a  buffing  wheel  for  coloring  and  no 
further  action  takes  place.  In  the  case  of  japanned  coating  it  is 
recommended  that  the  first  dip  be  made  in  a  solution  of  about  50 
per  cent,  benzine  and  50  per  cent,  japan.  This  thin  coating  insures 
a  perfect  body.  This  is  baked  on  very  hard  and  the  second  dip 
should  be  a  heavier  coating. 

282 


COLORING  AND  FINISHING  SHERARDIZED  ARTICLES       283 

For  lacquer  finish  no  special  operation  is  necessary,  as  it  will  de- 
posit as  readily  as  on  the  plain  material.  If  a  smooth  surface  is 
required  simply  buff  the  article  on  a  cloth  wheel  or  scratch  brush 
before  finishing. 

This  applies  to  large  articles  which  cannot  be  tumbled.  To  ob- 
tain the  smooth  surface  on  small  articles  for  plating  or  for  other 
purposes,  they  are  placed  in  a  tumbling  barrel.  For  dry  tumbling 
use  leather  meal  or  leather  chips,  operation  extending  anywhere 
from  two  to  ten  hours.  For  wet  tumbling  use  shot  on  light  ma- 
terial only. 


CHAPTER  XXXI 

Cost  of  Sherardizing  Material  per  Ton  with 
Different  Fuels 

A  GAS  burning  furnace  does  not  require  the  heavy  re- 
inforcement that  an  oil  burning  or  a  coke  furnace 
requires  because  it  is  not  under  as  much  pressure. 
It  has  further  been  found  that  gas  burning  furnaces  are  easier 
to  operate  but  more  expensive.  Fuel  oil  and  coke  are  the 
cheapest  known  fuels  in  the  East.  Where  natural  gas  is  available, 
this  by  far  is  the  cheapest  fuel.  The  ordinary  wear  and  tear  on 
these  furnaces  is  very  small,  due  to  the  fact  that  less  than  1000 
deg.  F.  is  required.  It  should  be  understood  that  as  little  structural 
iron  should  be  used  on  the  inner  part  of  the  furnace  as  possible,  to 
keep  from  warping.  A  coke  burning  furnace  requires  about  3000 
more  brick  than  the  ordinary  oil  and  gas  furnace,  due  to  the  fact 
that  the  fire  box  must  be  thoroughly  reinforced  for  high  pressure 
heating  and  retaining  of  heat,  but  with  this  equipment  there  are 
no  extra  installations  such  as  producer  gas  machines  and  fuel  oil 
machines  necessitate. 

Sherardizing  is  like  annealing  in  that  it  requires  a  small  amount 
of  labor,  and  that  unskilled  labor,  placed  under  proper  siipervision, 
can  operate  the  plant  as  successfully  as  a  high  priced  laborer. 

Cost  for  Fuel  Oil  Burning 

Per  ton 

Fuel  oil,  one  gallon  per  hour  per  burner,  3  burners  per  fur- 
nace, 30  gals,  per  day  of  10  hours,  at  5c  per  gal $1.50 

Zinc  dust,  average  deposit  4  Ibs.  per  100  Ibs.  of  material 
treated,  80  Ibs.  per  ton,  at  $5.75  per  100  Ibs.,  average 

market  price    4.60 

Labor,  two  men  at  15c  per  hour,  which  includes  the  labor  for 

cleaning,  pickling,  packing,  etc 3.00 

Total    $9.10 

284 


COST  OF  SHERARDIZING  MATERIAL  PER  TON  285 

Producer  Gas 

Per  ton 

Flynn  &  Dreffein's  guarantee,  cost  averaged  at  the  rate  of 
80  Ibs.  Pea  Coal,  equivalent  to  1,000  feet  of  illuminating 
gas,  at  7'5c  per  1,000;  consumption  of  furnace  4,000  ft. 
per  day  would  be  320  Ibs.  of  coal,  at  $4.50  per  ton $0.72 

Zinc  dust,  average  deposit  4  Ibs.  per   100  Ibs.  of  material 

treated,  80  Ibs.  per  ton  at  $5.75  per  100  Ibs 4,60 

Labor,  2  men  at'  15c  per  hour,  which  includes  labor  for  clean- 
ing and  pickling,  per  ton 3.00 


Total    $8.32 

Coke 

Per  ton 

Coke,  8  bu.  per  day  at  lOc  per  bu $0.80 

Per  ton 
Zinc  dust,  average  deposit  i  Ibs.  per  100  Ibs.  of  material 

treated,  80  Ibs.  per  ton,  at  $5.75  per  100  Ibs 4.GO 

Labor,  2  men  at  15c  per  hour,  which  includes  labor  for  clean- 
ing and  pickling 3.00 


Total    -$8.40 

Illuminating  Gas 

Per  ton 

Gas,  4,000  ft.  at  ?5c  per  1,000 $3.00 

Zinc  dmt,  average  deposit  4  Ibs.  per  100  Ibs.  of  material 

treated,  80  Ibs.  per  ton,  at  $5.75  per  100  Ibs 4.60 

Labor,  2  men  at  loc  per  hour,  which  includes  labor  for  clean- 
ing and  pickling 3.00 


Total $10.60 

This  being  a  patented  process  a  royalty  of  $2.50  per  ton  must 
be  added  for  the  cost  for  every  ton  of  material  treated.  With  a 
large  capacity  plant  the  above  cost  would  be  less,  due  to  saving 
both  in  fuel  and  labor. 

Disposal  of  Used  Zinc  or  Zinc  Residue 

When  sufficient  amount  of  zinc  oxide  has  accumulated  with  the 
zinc  to  warrant  disposal,  discontinue  the  adding  of  new  zinc,  and 


286  GALVANIZING  AND  TINNING 

by  extending  the  time  of  the  operation  or  increasing  the  tempera- 
ture, same  will  be  reduced  very  rapidly  until  about  20  per  cent, 
metallic,  at  which  time  it  should  be  disposed  of.  There  is  always 
a  market  for  this  material,  providing  no  sands,  flint  or  other  ma- 
terials are  mixed  with  the  zinc  for  coloring  purposes.  This  has 
been  one  of  the  objectionable  features  in  the  process,  and  very  de- 
ceiving to  the  public  in  giving  color  and  not  zinc  simply  for 
appearance. 


CHAPTER  XXXII 

Galvanizing  Specifications  and  Tests 

THE  following  specifications  applied  to  the  galvanized  over- 
head construction  material  purchased  by  the  Pennsylvania 
Eailroad  for  the  Philadelphia  electrification,  and  all  gal- 
vanized material  used  by  the  New  York,  New  Haven  &  Hartford 
Railroad  in  their  electrification  improvements  was  required  to  meet 
these  specifications  before  being  accepted. 

Specifications  for  Hot  and  Electro -Galvanizing 

This  specification  shall  apply  to  all  galvanized  iron  or  steel  ex- 
cept that  coated  with  zinc  by  the  Sherardizing  process. 

Coating 

The  galvanizing  shall  consist  of  a  continuous  coating  of  pure 
zinc  of  uniform  thickness,  and  so  applied  that  it  adheres  firmly 
to  the  metal.  The  finished  product  shall  be  smooth. 

Cleaning 

The  samples  shall  be  cleaned  before  testing,  first  with  carbona, 
benzine  or  turpentine,  and  cotton  waste  (not  with  a  brush),  and 
then  thoroughly  rinsed  in  clean  water  and  wiped  dry  with  clean 
cotton  waste. 

Solution  for  Testing  Coating 

The  standard  solution  of  copper  sulphate  to  be  used  in  testing 
shall  consist  of  commercial  copper  sulphate  crystals  dissolved  in 
cold  water,  about  in  the  proportion  of  thirty-six  parts,  by  weight, 
of  crystals  to  100  parts,  by  weight,  of  water.  The  solution  shall 
be  neutralized  by  the  addition  of  an  excess  of  chemically  pure 
cupric  oxide  (CuO).  The  presence  of  an  excess  of  cupric  oxide 
will  be  shown  by  the  sediment  of  this  reagent  at  the  bottom  of  the 
containing  vessel. 

The  neutralized  solution  shall  be  filtered  before  using  by  pass- 
ing through  filter  paper.  The  filtered  solution  shall  have  a  specific 
gravity  of  1.186  at  65  deg.  Fahr.  (reading  the  scale  at  the  level  of 

287 


288  GALVANIZING  AND  TINNING 

the  solution)  at  the  beginning  of  each  test.  In  case  the  filtered 
solution  is  high  in  specific  gravity,  clean  water  shall  be  added  to 
reduce  the  specific  gravity  to  1.186  at  65  deg.  Fahr.  In  case  the 
filtered  solution  is  low  in  specific  gravity,  filtered  solution  of  a 
higher  specific  gravity  shall  be  added  to  make  the  specific  gravity 
1.186  at  65  deg.  Fahr. 

As  soon  as  the  stronger  solution  is  taken  from  the  vessel  con- 
taining the  unfiltered  neutralized  stock  solution,  additional  crys- 
tals and  water  must  be  added  to  the  stock  solution.  An  excess  of 
cupric  oxide  shall  always  be  kept  in  the  unfiltered  stock  solution. 

Quantity  of  Solution 

Wire  samples  shall  be  tested  in  a  glass  jar  of  at  least  two  inches 
(2  in.)  inside  diameter.  The  jar  without  the  wire  samples  shall 
be  filled  with  standard  solution  to  a  depth  of  at  least  four  inches 
(4  in.).  Hardware  samples  shall  be  tested  in  a  glass  or  earthen- 
ware jar  containing  at  least  one-half  (!/£)  pint  of  standard  solu- 
tion for  each  hardware  sample. 

Solution  shall  not  be  used  for  more  than  one  series  of  four  im- 
mersions. 

Samples 

Not  more  than  seven  wires  shall  be  simultaneously  immersed, 
and  not  more  than  one  sample  of  galvanized  material  other  than 
wire  shall  be  immersed  in  the  specified  quantity  of  solution. 

The  samples  shall  not  be  grouped  or  twisted  together,  but  shall 
be  well  separated  so  as  to  permit  the  action  of  the  solution  to  be 
uniform  upon  all  immersed  portions  of  the  samples. 

Tests 

Clean  and  dry  samples  shall  be  immersed  in  the  required  quan- 
tity of  standard  solution  in  accordance  with  the  following  cycle 
of  immersions. 

The  temperature  of  the  solution  shall  be  maintained  between 
62  and  68  cleg.  Fahr.  at  all  times  during  the  following  test: 
First.         Immerse  for  one  minute,  wash  and  wipe  dry. 
Second.     Immerse  for  one  minute,  wash  and  wipe  dry. 
Third.       Immerse  for  one  minute,  wash  and  wipe  dry. 
Fourth.     Immerse  for  one  minute,  wash  and  wipe  dry. 
After  each  immersion  the  samples  shall  be  immediately  washed 


GALVANIZING  SPECIFICATIONS  AND  TESTS  289 

in  clean  water  having  a  temperature  between  62  and  68  deg.  Fahr., 
and  wiped  dry  with  cotton  waste. 

In  the  case  of  No.  14  galvanized  iron  or  steel  wire,  the  time  of 
the  fourth  immersion  shall  be  reduced  to  one-half  minute. 

Results  of  Tests 

After  the  tests  described  in  "Tests"  above,  no  bright  metallic 
copper  deposit  shall  show  on  the  samples. 

In  case  the  article  is  threaded,  the  thread  shall  be  clean  and  true 
after  galvanizing  and  shall  stand  at  least  one  immersion  in  the 
test  solution.  The  rest  of  the  article  shall  stand  the  specified  four 
immersions. 

The  threads  of  nuts,  except  those  galvanized  by  the  electrolytic 
process,  shall  be  cut  after  galvanizing,  and  the  threads  shall  not 
be  required  to  pass  the  tests. 

Copper  deposits  on  zinc,  or  within  one  inch  of  a  cut  end,  shall 
not  be  considered  causes  for  rejection. 

In  case  of  failure  of  only  one  wire  in  a  group  of  seven  wires 
immersed  together,  or  if  there  is  a  reasonable  doubt  as  to  the 
copper  deposit,  two  check  tests  shall  be  made  on  these  seven  wires 
and  the  lot  reported  in  accordance  with  the  majority  of  the  sets 
of  tests. 

Failure  to  Meet  Requirements 

Any  shipment  or  part  of  a  shipment,  the  samples  from  which 
fail  to  pass  the  above  requirements,  may  be  rejected. 

Testing  Galvanized  Products 

Obviously  the  only  final  durability  test  of  a  zinc  coating  is  the 
test  of  time  while  in  use  under  actual  conditions  of  exposure. 
This  method  however  takes  too  long  for  commercial  purposes  and 
some  other  means  of  making  comparative  tests  which  will  give 
prompt  results  must  be  adopted.  Several  such  tests  are  in  general 
use,  and  the  following  information  taken  from  a  booklet  entitled 
"The  History  and  Development  of  the  Galvanizing  Industry"  and 
reprinted  in  Metal  Industry  covers  the  subject  in  an  interesting 
manner : 

The  outward  appearance  of  any  galvanized  article  is  not  neces- 
sarily an  indication  of  its  excellence.  This  statement  may  be 
taken  as  a  general  rule  applying  to  articles  coated  by  e'ither  of  the 
galvanizing  processes  mentioned  herein. 


290  GALVANIZING  AND  TINNING 

For  over  forty  years  prior  to  1880  the  hot  galvanizing  process, 
which  was  practically  the  only  galvanizing  process  in  commercial 
use  prior  to  that  time,  was  believed  to  produce  uniform  results. 
It  was,  therefore,  not  deemed  necessary  to  test  such  coatings  by 
any  other  means  than  that  of  durability  under  actual  weather  con- 
ditions. Observations  made  by  Sir  W.  H.  Preece,  chief  of  the 
British  Post  Office  Telegraphs,  led  him  to  see  the  necessity  of  a 
test  for  zinc  coatings  on  telegraph  wires. 

Preece,  or  Copper  Sulphate  Test 

Between  1880  and  3890  Preece  devised  what  is  known  as  the 
"copper  sulphate  test"  for  galvanized  articles,  and  this  test  has 
until  recently  been  accepted  as  the  final  word  regarding  the  quant- 
ity of  any  galvanized  product.  This  test  has  been  modified  and 
standardized  in  the  United  States,  notably  by  the  chief  engineer 
of  the  Western  Union  Telegraph  Company,  and  has  been  quite 
generally  adopted  by  producers  and  consumers  of  galvanized  prod- 
ucts, such  as  wire,  sheets,  line  material,  etc. 

The  original  Preece  test  consisted  in  the  immersion  of  the  gal- 
vanized article  in  a  saturated  solution  of  copper  sulphate  for  a 
period  of  one  minute,  removing,  rinsing  in  water,  wiping  and 
again  immersing  in  the  copper  sulphate  solution.  The  number 
of  immersions  which  the  article  could  withstand  before  showing 
bright  copper  on  the  underlying  steel  or  iron  was  taken  as  an 
indication  of  the  excellence  of  the  zinc  coating. 

Temperature  Important 

As  at  present  standardized  careful  preparation  of  the  copper 
sulphate  solution  is  necessary.  The  solution  is  brought  to  a  den- 
sity of  1.186  specific  gravity  at  a  temperature  of  65  degs.  Fahr. 
This  solution  is  usually  treated  with  a  small  portion  of  cupric 
oxide  to  neutralize  any  free  acid  which  might  exist  in  the  copper 
sulphate  crystals.  Galvanized  articles  are  first  to  be  cleaned  of 
dirt  and  grease  by  immersion  in  gasoline  or  benzine,  then  rinsed 
in  water  and  wiped  dry. 

After  this  preparatory  treatment  the  articles  are  given  succes- 
sive one-minute  immersions  in  the  standard  copper  sulphate  liquor, 
held  at  a  temperature  of  from  65  to  70  degs.  Fahr.,  rinsed  thor- 
oughly in  water  and  wiped  dry  after  each  immersion.  The  samples 
are  to  be  carefully  scrutinized  after  each  immersion,  and  if  spots 


Wallace  &.  Imhaff 

GALVANIZING  SPECIFICATIONS  AND  TESTS  291 

of  a  clear  copper  color  are  observed,  the  coating  is  said  to  have 
i'ailed.  The  number  of  successive  immersions  which  the  article 
will  withstand  without  showing  indications  of  clear  copper  is 
taken  as  an  indication  of  the  quality  of  the  coating.  A  new  por- 
tion of  solution  is  to  be  taken  for  testing  each  article. 

Limitations  of  Copper  Sulphate  Test 

It  will  be  noted  that  the  Preece,  or  copper  sulphate  test,  de- 
termines only  the  thickness  of  the  zinc  coating  at  its  thinnest  por- 
tion. It  is,  therefore,  not  in  any  sense  a  determination  of  how 
much  or  how  little  zinc  is  deposited  on  the  article  under  test.  It 
is  well  known  that  the  copper  sulphate  test  is  unsuitable  for  test- 
ing Sherardized  articles,  and  it  is  a  fact,  however  not  generally 
known,  that  the  copper  sulphate  does  not  attack  zinc  coatings 
deposited  electrically,  and  by  hot  galvanizing  methods  at  equal 
rates.  It  has  been  further  demonstrated  that  the  different  tem- 
peratures of  the  molten  bath  and  different  methods  of  cooling 
articles  galvanized  in  molten  zinc  show  entirely  unreliable  results 
when  subjected  to  the  copper  sulphate  test.  From  these  remarks 
it  will  be  seen  that  it  is  unfair  to  test  competitively  zinc  coatings 
applied  by  Sherardizing,  hot  galvanizing  and  electro-galvanizing 
methods. 

Lead  Acetate  Test 

Owing  to  the  unsatisfactory  results  secured  by  means  of  the 
copper  sulphate  test,  in  a  measure  pointed  out  in  the  preceding 
paragraphs,  an  accurate  quantitative  test  for  galvanized  products 
has  been  devised.  The  lead  acetate  test,  as  it  is  known,  was  re- 
cently originated  by  Prof.  W.  H.  Walker,  of  the  Massachusetts 
Institute  of  Technology,  Boston. 

The  test  is  designed  to  show  the  weight  of  actual  coating  cov- 
ering products  galvanized  by  any  of  the  well-known  methods.  It 
takes  into  consideration  the  impurities  residing  in  the  coating  and 
the  main  impurity  usually  found,  i.  e.,  iron,  may  be  determined 
if  desired.  In  practice,  however,  it  is  seldom  carried  out  to  this 
extent.  The  solution  employed  removes  from  the  articles  both  the 
zinc  and  zinc-iron  alloys  present.  The  accurate  weight  before  and 
after  testing  furnishes  the  basis  for  computing  the  quantitative 
value  of  the  coating.  It  is  unnecessary  to  take  the  time  of  sample 
immersion  accurately,  in  which  respect  the  lead  acetate  test  differs 


292  GALVANIZING  AND  TINNING 

i'rom  the  copper  sulphate  test;  however,  the  weighings,  which  must 
he  accurate  to  one  milligram,  require  considerable  time  and  care. 
The  lead  acetate  solution  is  prepared  as  follows: 

Dissolve  3  pounds  of  commercial  lead  acetate  crystals 
(Pb  (C2H302)2-f-3H20)  in  one  gallon  of  distilled  water  and  add 
1  oz.  litharge  (PbO).  After  complete  solution  of  the  lead  acetate, 
the  mixture  should  be  stirred  vigorously  and  any  undissolved  resi- 
due allowed  to  settle.  The  clear  liquor  is  then  poured  off  and  the 
solution  is  ready  for  use.  It  is  unnecessary  to  maintain  any  ac- 
curate temperature  of  solution  as  is  required  in  the  copper  sulphate 
test,  and  the  solution  may  be  used  for  several  tests  without  renewal. 
until  such  time  as  the  action  becomes  too  slow. 

Samples  of  galvanized  product  are  first  to  be  thoroughly  cleaned 
of  oil  and  dirt  by  rinsing  in  benzine  or  in  gasoline,  then  rinsing  in 
cold  water  and  dried  with  clean  cotton  waste.  The  sample  should 
next  be  weighed  to  an  accuracy  of  one  milligram,  and  the  weight 
noted.  The  sample  is  then  ready  for  immersion  in  the  lead  acetate 
solution. 

The  length  of  time  during  which  the  sample  is  under  treatment 
is  usually  about  three  minutes,  although  it  may  be  left  in  for  a 
longer  period  without  affecting  the  result.  These  immersions  should 
be  repeated  until  all  of  the  coating  has  been  removed  and  the 
sample  exhibits  the  clean  steel  underneath.  A  short  experience  will 
enable  the  operator  to  tell  with  certainty  when  all  of  the  coating 
has  been  removed.  After  each  immersion  in  the  lead  acetate  solu- 
tion, the  flocculent  or  loose  coating  of  spongy  lead  which  is  de- 
posited must  be  carefully  removed ;  for  this  purpose  it  is  usual  to 
employ  a  small,  soft  bristle  brush,  care  being  taken  that  no  lead 
is  "burnished"  over  the  zinc  coating.  If  any  spots  of  lead  are 
noted,  which  the  solution  does  not  remove,  the  careful  use  of  a 
sharp  knife  is  necessary.  When  the  coating  is  all  removed,  the 
sample  is  then  dried  by  immersion  in  alcohol  and  ignition,  or  by 
placing  over  a  small  steam  coil.  Final  weight  of  the  sample  is  then 
taken  and  noted. 

If  it  is  desired  to  estimate  the  amount  of  iron  in  the  coating, 
the  samples  must  be  rinsed  in  clean  water  contained  in  a  beaker. 
care  being  taken  that  all  lead  acetate  and  solution  washings  are 
saved.  The  lead  acetate  and  the  wash  solutions  may  be  put  to- 
gether and  filtered,  and  slightly  acidified  with  sulphuric  acid ;  a 
few  particles  of  granulated  zinc  should  then  be  added,  when  the 


GALVANIZING  SPECIFICATIONS  AND  TESTS  293 

amount  of  iron  is  ascertained  by  titrating  the  solution  with  a 
standard  solution  of  potassium-permanganate.  The  lead  may  be 
balled  and  squeezed  with  the  fingers,  and  saved  if  desired. 

The  lead  may  be  weighed  and  the  amount  of  zinc  coating  re- 
moved may  be  calculated  from  the  weight  of  the  lead,  the  preferable 
manner  of  determining  the  amount  of  coating  on  the  sample  under 
test  is  as  follows:  Deduct  the  final  weight  of  sample  after  treat- 
ment in  the  lead  acetate  solution  from  the  original  weight  of  the 
galvanized  piece.  Divide  the  net,  weight  of  coating  so  obtained  by 
the  weight  of  the  bare  or  uncoated  sample,  whence  the  per  cent,  of 
loss  in  weight  is  ascertained  nearly  enough  for  all  practical  pur- 
poses. Apply  the  per  cent,  loss  figure  to  2,000  Ibs.  representing  a 
ton  of  the  articles  in  question.  This  will  give  the  pounds  of  coat- 
ing per  ton  of  product. 

Next,  ascertain  by  close  measurement  or  estimation  how  many 
sq.  ft.  of  surface  there  are  in  a  ton  of  2,000  Ibs.  of  the  articles 
under  examination,  reducing  the  Ibs.  coating  per  ton  found  by  the 
application  of  the  percentage  figure,  to  ounces  by  multiplying  by 
16.  Having  the  ounces  of  coating  per  ton  and  the  number  of  sq. 
ft.  of  surface  per  ton,  divide  the  former  figure  by  the  latter,  and 
find  the  ounces  per  sq.  ft. ;  this  is  usually  a  decimal  figure.  The 
ounces  of  coating  per  sq.  ft.  gives  a  unit  which  may  be  used  for  the 
purpose  of  comparing  the  values  of  coating  on  different  styles  and 
kinds  of  galvanized  product. 

Samples  of  galvanized  articles  which  are  to  be  given  the  lead 
acetate  test  must  be  above  all  things  smoothly  galvanized,  without 
adhering  lumps  or  drops  of  spelter,  since  these  imperfections  would 
lead  to  erroneous  conclusions  by  adding  to  the  net  weight  of  coating 
particles  of  metal  not  evenly  distributed,  wherefore  the  resultant 
ounces  per  sq.  ft.  would  be  too  high ;  it  should  be  carefully  observed 
that  all  portions  of  the  galvanized  article  are  coated,  unless  the  un- 
coated areas  are  left  out  of  the  area  figure  per  ton. 

Caustic  Soda  Test 

Prof.  Walker  has  rendered  further  service  to  those  interested  in 
testing  galvanized  materials  by  supplying  a  test  which  will  show 
the  presence  or  absence  of  pores  or  cracks  in  zinc  coatings. 

A  strong  solution  of  caustic  soda  in  water  is  heated  to  a  tempera- 
ture of  about  210  degs.  Fahr.,  and  the  galvanized  article  suspended 
in  this  solution  by  a  string  or  other  non-metallic  suspension.  If 


294  GALVANIZING  AND  TINNING 

pin  holes  or  cracks  exist  in  the  coating,  bubbles  or  hydrogen  will  be 
observed  to  come  from  the  surface  of  the  article  at  these  points, 
while  if  there  are  no  pores  or  cracks  in  the  coating,  no  action  will 
be  observed.  The  caustic  soda  test  will  show  whether  or  not  the 
coating  has  cracked  when  the  galvanized  article  is  bent  after  gal- 
vanizing. 

In  a  recent  issue  of  The  Iron  Age  Mr.  Samuel  Trood  has  also 
given  special  consideration  to  the  use  of  the  various  texts  from  the 
standpoint  of  an  expert  on  Sherardizing. 

The  Preece  Test 

The  solution  is  made  up  by  dissolving  36  parts  by  weight  of 
commercial  copper  sulphate  crystals  in  100  parts  of  water  and  then 
neutralizing  by  the  addition  of  excess  of  chemically  pure  cupric 
oxide.  The  presence  of  excess  oxide  is  indicated  by  the  undissolved 
part  settling  to  the  bottom  of  the  vessel. 

It  is  difficult  and  takes  much  time  to  get  the  copper  sulphate  into 
solution  at  room  temperature,  even  if  the  solution  is  agitated  by 
blowing  air  through  it,  or  if  the  crystals  are  suspended  in  a  basket 
near  the  top  of  the  solution.  Heating  will  greatly  accelerate  the 
rate  of  solution,  and  in  this  way  a  solution  can  be  prepared  a  little 
stronger  than  that  desired,  the  final  exact  adjustment  being  after- 
ward made  by  diluting  with  water.  To  do  this  accurately  and  rap- 
idly, add  a  certain  number  of  cubic  centimeters  of  water  to  about  5 
liters  of  solution,  and  note  how  many  thousandths  change  this  pro- 
duces in  the  specific  gravity.  One  or  two  further  additions  will 
then  suffice  to  get  an  accurate  adjustment  of  the  strength. 

It  was  noted  that,  after  the  finished  solution  has  been  filtered 
off  from  the  copper  oxide,  CuO,  in  the  bottom  of  the  stock  bottle, 
there  is  separated  out,  sometimes  a  reddish  or  sometimes  a  bulky 
pale  green  precipitate,  after  the  solution  has  stood  for  a  consider- 
able time,  due  to  some  impurity,  or  it  may  be  to  some,  basic  salt  of 
copper.  It  probably  does  not  affect  the  strength  or  neutrality  of 
the  solution  appreciably,  since  the  quantity  is  not  great.  How- 
ever, for  very  accurate  work  it  might  be  desirable  to  determine  the 
effect  of  this  change,  and  whether  it  is  desirable  to  always  use  a 
solution  recently  filtered  off  from  CuO  sediment. 

The  descriptions  of  the  test  specify  that  the  strength  of  the  solu- 
tion shall  be  1.186  at  65  deg.  Fahr.  It  would  be  desirable  to  know 
the  permissible  variation  from  this,  that  is,  the  error  due  to  having 


GALVANIZING  SPECIFICATIONS  AND  TESTS  295 

the  strength  1.184  or  1.188,  for  example;  further,  it  would  simplify 
the  operation  of  making  up  the  solution,  if  only  an  occasional  one 
is  made  up  and  means  for  getting  the  temperature  exactly  adjusted 
are  not  convenient,  to  know  what  specific  gravity  to  aim  for  if  the 
temperature  is  70  cleg,  or  80  deg.  Fahr.  After  the  strength  has  once 
been  adjusted,  the  temperature  at  which  the  solution  is  used  has  an 
effect  upon  the  accuracy  of  the  test.  This  will  be  taken  up  in  an- 
other paragraph. 

Manipulation  of  the  Test 

There  does  not  seem  to  be  published  information  on  the  one 
point  that  determines  whether  or  not  the  operator  will  have  suc- 
cess when  he  attempts  to  apply  the  Preece  test  to  Sherardized  and 
alloy-coated  articles.  This  is  that  the  specimen  must  be  brushed 
instead  of  wiped,  in  removing  the  loose  copper  after  each  dip. 

The  copper  which  replaces  the  zinc  on  a  galvanized  coating  is  in 
such  a  loose  non-adherent  form  that  it  can  be  easily  wiped  off  with 
cotton  waste,  but  that  which  forms  on  Sherardized  coatings  is  more 
adherent,  probably  due  to  the  slower  rate  at  which  zinc-iron  alloy 
precipitates  copper  from  the  solution  as  compared  with  zinc  itself. 
Further,  the  Sherardized  surface  is  rough  so  that,  if  the  specimen 
is  wiped  with  waste,  the  copper,  instead  of  being  removed,  is  rubbed 
into  the  hollows  of  the  surface.  This  copper  then  protects  the  still 
remaining  underlying  alloy  from  further  action  of  the  solution  and 
the  test  is  spoiled.  The  further  solution  of  the  protected  alloy  is 
retarded  so  that,  if  the  dips  are  continued,  the  specimen  will  appear 
to  stand  more  dips  than  correspond  to  the  thickness  of  coating 
present  or  even  may  stand  an  indefinite  number  of  dips.  On  the 
other  hand,  if  the  operator  has  not  had  some  experience,  he  may 
interpret  this  premature  appearance  of  copper  as  a  failure,  since 
after  several  burnishings  by  waste,  the  copper  on  alloy  may  take  a 
polish  that  resembles  closely  the  appearance  of  copper  formed  on  the 
iron.  By  removing  the  copper  after  each  dip  by  vigorous  brush- 
ing with  plenty  of  water,  as  under  a  faucet,  the  risk  of  rubbing  it 
into  the  hollows  is  practically  eliminated. 

In  a  Sherardized  specimen  the  portion  of  the  coating  next  to 
the  iron  shows  a  lighter  color  during  the  Preece  test  than  that 
nearer  the  surface.  For  this  reason,  then,  after  brushing  and  dry- 
ing, a  light  patch  shows  up  on  a  darker  background,  it  indicates  that 
the  coating  is  thin  at  that  point  and  failure  is  to  be  expected. 


296  GALVANIZING  AND  TINNING 

Sometimes,  due  to  imperfect  brushing,  copper  will  form  on  the 
surface  of  the  coating,  as  mentioned,  but  this  copper  can  be  dis- 
tinguished from  the  copper  formed  on  the  iron  at  the  point  of 
failure  in  several  ways.  The  copper  at  the  failure  is  lighter  in 
color  than  that  due  to  improper  brushing,  it  is  surrounded  by  an 
area  of  light  colored  coating  and  it  forms  in  the  hollows  or 
"valleys"  of  the  coating,  while  the  other  forms  on  the  higher  por- 
tions or  "hill  tops."  This  last  difference  is  always  noticeable  under 
a  magnifying  glass,  but  it  can  be  distinguished  by  the  eye  after  a 
little  practice. 

The  regular  Preece  test  was  made  on  some  No.  16  gauge  wire 
which  had  been  given  a  Sherardized  coat  in  such  a  manner  that  it 
was  very  smooth.  It  was  noticed  that  the  copper  which  formed 
could  be  wiped  off  with  waste  and  that  the  test  would  give  the  same 
results  whether  the  wiping  was  done  by  waste  or  by  brush.  In 
order  to  determine  whether  the  character  of  the  coat  affected  this, 
similar  tests  were  made  on  Sherardized  sheet.  One  sheet  had  a 
rough  coat  while  the  other  was  smooth.  Both  were  dipped  at  the 
same  time  in  the  same  solution  and  both  were  wiped  with  waste. 
After  the  fourth  dip  the  copper  which  had  deposited  on  the  rough 
specimen  was  rubbed  into  the  crevices  of  the  surface  and  gave  a 
topperish  color  to  the  specimen.  Large  patches  of  this  copper  were 
burnished  to  a  metallic  polish.  The  copper  which  had  deposited 
on  the  smooth  piece  showed  practically  no  tendency  to  remain,  as 
there  were  few  cracks  or  hollows  in  which  it  could  form. 

A  specimen  of  Sherardized  sheet  2^x4  in.,  with  a  very  thick 
Sherardized  coating,  was  dipped  info  a  solution  2  inches.  One-half 
of  the  tested  part  was  brushed  after  each  dip  and  the  other  half 
was  wiped  with  waste.  After  the  third  dip  fine  copper  began  to 
collect  on  the  wiped  half  in  the  crevices  of  the  coat  and  the  amount 
increased  after  each  dip.  The  brushed  side  kept  a  uniform  dark 
color  through  the  entire  test  showing  no  deposition  of  copper.  The 
copper  formed  on  the  wiped  half  became  thicker  after  each  dip. 
The  Sherardized  coating  where  it  was  not  protected  by  this  layer 
of  copper  became  thinner  and  eventually  failed.  The  appearance 
of  the  coating  on  the  brushed  half  was  uniform  and  showed  no  in- 
dication of  failure.  The  elevated  deposit  of  copper  on  the  wiped 
half  could  be  flaked  off.  The  premature  failure  of  the  wiped  half 
was  due  to  the  accelerating  action  of  the  heavy  elevated  deposit  of 
copper;  that  is  to  say,  the  burnished  copper  on  the  alloy  protects 


GALVANIZING  SPECIFICATIONS  AND  TESTS  297 

only  the  alloy  directly  beneath  it,  but  accelerates  the  solution  of 
immediately  adjoining  areas  of  alloy.  The  elevated  copper  had  a 
nodular  rough  surface  while  that  deposited  on  the  iron  at  the 
failure  was  smooth  and  bright. 

Temperature  of  the  Solution 

The  American  Steel  &  Wire  Company  specifies  that  in  carrying 
out  the  dip  test  the  temperature  of  the  solution  must  be  between 
Go  and  70  deg.  Fahr.,  while  the  American  Telephone  &  Telegraph 
Company  specifies  62  to  68  deg.  Fahr.  It  is  of  interest  to  know  the 
percentage  of  error  due  to  temperature  variations,  especially  when 
only  an  occasional  test  has  to  be  made,  since  it  may  then  take  much 
more  time  to  arrange  to  get  the  right  temperature  than  to  run  the 
tests.  Results  obtained  with  solution  at  different  temperatures, 
75  c.c.  of  solution  being  used,  are : 

Average  loss, 
Temperature  gr.  per  sq.  in. 

55    deg.    F 0.0201 

65    deg.    F 0.03185 

75    deg.    F 0.034") 

85   deg.   F 0.0397 

These  figures  show  that  if  a  specimen  is  very  close  to  the  point 
of  rejection  a  difference  of  10  degrees  may  easily  mean  rejection  or 
acceptance  for  the  same  actual  thickness  of  coating. 

Consideration  of  Objections  to  Preece  Test 

The  accuracy  of  the  Preece  test  has  been  called  into  question  by 
Patrick  and  Walker  (Journal  of  Industrial  and  Engineering  Chem- 
istry, April,  1911),  for  the  reason  that  the  rate  at  which  CuS04 
solution  dissolves  zinc  is  different  from  the  rate  of  solution  for 
zinc-iron  alloy.  The  rate  of  solution  is  slower  for  the  zinc-iron 
alloy  because  of  its  lower  potential  as  compared  with  zinc.  But  this 
lower  potential  would  seem  to  indicate  a  correspondingly  slower 
corrosion  by  atmospheric  influence,  so  that  the  number  of  dips  in 
a  corrosive  solution  that  a  specimen  will  stand  is  a  fairer  indica- 
tion of  its  resistance  to  corrosion,  and  therefore  the  usefulness  of 
the  coating,  than  the  actual  weight  of  the  zinc  present.  It  is  a 
determined  fact  that  less  weight  of  zinc  in  the  form  of  Sherardizcd 
coat  will  afford  protection  equal  to  a  greater  amount  of  zinc  in  the 
form  of  a  hot  or  electrogalvanized  coating. 

Determinations  have  been  made  of  the  relative  rate  of  solution 


298  GALVANIZING  AND  TINNING 

of  several  kinds  of  coating  in  the  standard  CuS04  solution  with  the 
following  results: 

Loss.  gr.  per 
Specimen  sq.  in.  per  dip 

Hot  galvanized  wire 0.0135 

Alloy  coated  nail    (Sherardized)  . 0.0082 

Sherarduct    0.0109 

Galvaduct     0.0131 

It  is  evident  that  the  Sherardized  coat  dissolves  materially  more 
slowly. 

In  comparing  one  specimen  of  hot  galvanized  material  with  an- 
other, there  may  be  a  slight  discrepancy  in  the  relation  between 
the  number  of  dips  and  the  actual  weight  of  coating.  This  is  due 
to  the  fact  that  in  different  specimens  of  hot  galvanizing  the  ratio 
between  alloy  and  pure  zinc  present  may  vary  from  something  like 
1  of  alloy  to  4:  of  zinc,  to  1  of  alloy  to  10  of  zinc.  Again,  it  may 
be  fairly  assumed  that  the  important  thing  to  know  is  the  number 
of  dips  the  specimen  will  stand  rather  than  the  weight  of  material 
present.  If,  however,  some  buyer  or  manufacturer  should  consider 
weight  the  only  factor  of  importance,  it  is  evident  that  a  difference 
of  rate,  as  indicated  in  the  above  table,  is  not  so  serious  when  it  is 
borne  in  mind  that  it  affects  only  14  to  1/10  of  the  coating; 
further,  when  the  Preece  test  is  used  as  a  regular  commercial  con- 
trol by  some  buyer  or  manufacturer,  the  articles  compared  from 
day  to  day  are  probably  usually  so  made  that  the  variation  in  the 
proportion  of  alloy  present  is  not  a  maximum  one. 

In  the  same  article,  Patrick  and  Walker  assert  that  the  end  point 
is  unreliable.  As  far  as  Sherardized  articles  are  concerned,  prac- 
tically all  of  this  uncertainty  as  to  the  end  point  arises  from  the 
fact  that  the  specimen  is  not  brushed  properly.  The  importance 
of  this  has  been  discussed  under  "Manipulation  of  the  Test."  It  is 
true,  however,  that  it  takes  more  practice  and  more  careful  dis- 
crimination to  use  the  Preece  test  for  Sherardized  articles  than  for 
hot  or  electrogalvanized  objects. 

In  order  to  get  additional  proof  that  really  adherent  copper  de- 
posits only  upon  iron  and  not  upon  alloy,  specimens  were  prepared 
and  examined  under  the  microscope.  It  was  noted  that  the  only  bright 
copper  on  the  brushed  specimen  was  on  the  iron,  while  the  thin 
alloy  surrounding  the  place  of  failure  showed  none  whatever.  Be- 
fore brushing  there  was  copper  on  this  alloy. 

Sellers  of  hot  galvanized  ware  have  raised  objection vto  permitting 


GALVANIZING  SPECIFICATIONS  AND  TESTS  299 

the  brushing  of  samples  of  Sherardized  ware,  in  carrying  out  the 
Preece  test.  As  long  as  there  is  any  coating  left  the  brushing  can 
certainly  do  nothing  that  would  make  the  Sherardized  article  show 
up  better  than  it  should ;  if  anything  it  would  remove  some  of  the 
coating  and  hasten  the  failure,  to  which  the  sellers  of  galvanized 
ware  would  certainly  not  object. 

The  only  possible  contentions  of  the  hot  galvanized  ware  sellers 
would  then  be  that  the  brushing  might  remove  copper  that  is  de- 
posited upon  iron.  According  to  observations  made  on  this  point, 
only  the  most  violent  brushing  will  do  this  and  there  is  not  the 
slightest  difficulty  in  avoiding  it.  The  use  of  the  stiffest  brush 
that  could  be  bought  in  a  local  drug  store  did  not  bring  about  the 
removal  of  this  copper,  and  a  much  softer  brush  is  perfectly  suffi- 
cient to  give  the  samples  all  the  brushing  they  need,  if  only  a 
burnishing  effect  is  avoided. 

Probably  the  only  way  in  which  there  is  danger  of  removing 
copper  from  iron  is  a  bending  back  and  forth  or  other  considerable 
distortion  of  the  specimen ;  or,  after  the  coating  has  been  removed 
and  the  next  dip  would  deposit  copper  and  iron,  to  get  the  specimen 
dirty  or  greasy  by  using  a  greasy  or  soapy  brush  or  handling  with 
the  hands.  If  the  sample  is  laid  upon  a  board,  in  brushing,  as  may 
be  desirable  with  light  flexible  objects,  in  order  not  to  scale  off  any 
copper,  the  board  should  of  course  be  free  from  soap,  grease,  dirt 
or  chemicals. 

The  Lead  Acetate  Test 

In  preparing  the  solution  used,  difficulty  was  found  in  getting 
the  prepared  quantity  of  lead  acetate  into  solution.  It  is  true  that 
by  heating  this  solution  would  be  indicated.  One  difficulty  en- 
countered in  working  the  test  was  due  to  the  deposition  of  adherent 
lead  on  Sherardized  samples  immediately  on  immersing,  particularly 
those  coated  by  dust.  This  adherent  lead  cannot  be  wiped  off  and 
protects  the  underlying  coating  from  going  into  solution.  The 
area  of  adherent  lead  on  some  specimens  was  over  90  per  cent,  of 
the  total  surface. 

Before  the  remedy  for  obviating  the  formation  of  adherent  lead 
had  been  found,  it  was  attempted  to  determine  the  loss  of  weight 
per  dip.  Instead  of  a  loss,  a  gain  in  weight  was  found,  showing  con- 
clusivelv  that  adherent  lead  was  formed.  Test  pieces  consisting  of 
Sherardized  nails  with  the  points  cut  off  were  used.  These  were 


300  GALVANIZING  AND  TINNING 

immersed  each  time  to  constant  depth.  The  area  of  the  surface  ex- 
posed was  therefore  constant  in  each  dip.  The  nails  were  cleaned 
in  gasoline,  washed  and  dried ;  one-minute  dips ;  brushed  lightly  and 
dried  after  each  dip. 

During                                         Nail  No.  1,  Nail  No.  2, 

dip  No.                                     gain  in  grams  gain  in  grams 

1 0.0011  0.0014 

2 0.0024  0.0020 

3 0.0028  0.0014 

4 0.0010  0.0003 

A  similar  nail  was  dipped  into  the  solution  and  only  adherent 
lead  formed.  The  nail  was  removed  and  a  knife  blade  scraped 
lightly  across  the  surface  and  replaced.  Loose,  black  crystalline 
lead  immediately  formed  on  the  scratched  portion,  while  none 
formed  on  the  other  parts  of  the  nail. 

Two  nails  similar  to  those  previously  mentioned  were  dipped  in 
the  same  manner  after  they  had  been  brushed  with  a  dry  brush  and 
wiped  with  a  dry  towel.  The  deposition  of  loose  lead  in  this  case 
took  place  in  spots,  but  covering  the  lesser  part  of  the  surface. 
These  spots  grew  slowly  during  the  dip.  The  brushing  after  each 
dip  was  done  lightly. 

During  Nail  No.  1,  Nail  No.  2, 

dip  No.  loss  in  grams  loss  in  grams 

1 0.0008  0.0036 

2 0.0018  0.0020 

3 0.0017  0.0051 

As  will  be  seen  from  the  next  determination,  these  are  not 
normal  results.  Several  other  devices  were  tried  to  bring  about 
the  proper  action  of  the  solution.  The  specimens  were  thoroughly 
moistened,  a  hot  solution  was  tried,  the  specimens  were  moved 
around  in  the  solution,  but  no  results  were  obtained. 

In  the  next  test  the  sample  was  treated  before  dipping  with  about 
20  per  cent,  acetic  acid  for  about  20  seconds,  or  until  a  distinct 
evolution  of  gas  took  place  over  its  entire  surface.  After  washing 
and  drying  it  was  dipped  and  weighed  as  in  the  previous  test.  The 
deposition  of  loose  lead  took  place  over  the  entire  surface  im- 
mediately after  immersion. 


During 
dip  No. 

Nail  No.  3, 
Loss  in  grams 
00201 

Nail  No.  3, 
Loss  grams 
per  sq.  in. 
00199 

2 

o  OK;:! 

0.0161 

3 

0  0138 

0.0137 

4..  . 

.  .    0.0141 

0.0140 

GALVANIZING  SPECIFICATIONS  AND  TESTS  301 

A  similar  test  with  a  larger  nail,  dipped  in  acetic  acid  before 
putting  into  the  lead  acetate  solution,  gave  the  following  results : 

During  Loss  grams 

dip  No.                                     Loss  in  grams  per  sq.  in. 

1 0.0120  0.0235 

2 0.0084  0.0165 

3 0.0085  0.0167 

4 0.0092  0.0180 

5 0.0080  0.0174 

6 0.0086  0.0169 

Instead  of  dilute  acetic  acid,  very  dilute  hydrochloric  acid  can 
also  be  used,  about  10  per  cent.,  and  the  specimen  immersed  in  this 
about  10  seconds.  It  is  probable  that  the  reason  that  the  lead 
acetate  solution  does  not  act  properly  at  the  start  is  that  there  is 
some  zinc  or  iron  oxide  on  the  surface  of  the  object. 

Patrick  and  Walker  do  not  approve  of  a  "dip"  method  of 
testing  the  thickness  of  a  coating,  no  matter  what  solution  is  used, 
but  believe  that  the  veight  of  the  coating  should  be  determined, 
cither  by  weighing  the  had  deposit  or  by  noting  the  loss  of  weight 
of  the  specimen.  Either  of  these  methods  takes  more  time  than 
that  of  counting  dips,  and  the  method  of  collecting,  drying  and 
weighing  the  lead  seems  especially  cumbersome  for  a  routine  works 
test.  The  calculation  of  the  results  will  take  time  also,  unless 
there  are  a  great  number  of  samples  of  the  same  shape  and  size  to 
be  tested. 

Preece  and  Acetate  Methods  Compared 

1.  For  commercial  testing  the  Preece  method  can  be  satisfac- 
torily used  for  Sherardized  as  well  as  for  hot  dip  and  electrogalvan- 
ized  articles,  if  the  specimens  are  brushed  properly.    It  takes  more 
practice  to  detect  the  end  point  for  testing  Sherardized  goods. 

2.  When  used  as  a  dip  method  the  lead  acetate  test  has  the  ad- 
vantage of  showing  the  end  point  with  less  practice  on  the  part  of 
the  operator.     It  is  troublesome  for  Sherardized  articles  since  the 
samples  must  be  dipped  in  acid,  as  described,  in  order  that  the  test 
can  be  worked. 

3.  The  lead  acetate  solution  removes  about  1.6  times  as  much 
coating  per  dip  as  the  copper  sulphate  solution.     It  would  be  de- 
sirable, in  order  to  prevent  confusion,  to  adjust  the  solution,  if 
possible,  so  that  a  dip  removes  the  same  quantity  in  both  cases.    If 
a  weaker  solution  is  used  in  order  to  reduce  the  rate  of  solution 


302  GALVANIZING  AND  TINNING 

for  the  lead  acetate  solution  there  may  be  more  trouble  with  the 
formation  of  adherent  lead. 

4.  As  a  testing  method  for  scientific  investigations  to  determine 
the  exact  weight  of  coating  the  lead  acetate  determination  has  the 
advantage  that  it  removes  the  coating  without  depositing  anything 
on  the  iron,  resulting  in  an  accurate  determination.     However  the 
error  due  to  the  small  amount  of  copper  replacing  iron   cannot 
be  material  if  it  is  desired  to  use  the  copper  sulphate  solution  in 
order  to  determine  the  loss  of  weight  of  the  specimen. 

5.  The  lead  acetate  method  affords  a  means  of  determining  the 
percentage  of  iron  in  the  coating.    This  is  not  essential  for  routine 
factory  testing,  and  in  fact  the  iron  determination  would  be  too 
troublesome  for  regular  works  control. 

6.  If  it  does  not  seem  possible  or  desirable  to  overcome  the  ob- 
jections of  the  sellers  of  hot  galvanized  ware  to  brushing  Sher- 
ardized  samples  during  the  Preece  test,  the  lead  acetate  method 
may  be  a  useful  substitute  or  at  any  rate  a  good  check  method  to 
show  that  brushing  does  not  result  in  too  favorable  indications  for 
Sherardized  goods  when  tested  by  the  Preece  method. 

7.  It  does  not  seem  justifiable  to  concur  in  Patrick  and  Walk- 
er's recommendation  to  substitute  a  weighing  method  for  the  dip 
method  for  commercial  purposes,  or  to  substitute  the  lead  acetate 
dip  method  for  the  copper  sulphate  method. 

Electrolytic  Methods 

Some  experimental  work  was  carried  on  which  showed  that  by 
removing  a  Shera-rdized  coating  by  electrolysis  in  a  solution  of 
potassium  nitrate  the  ampere-minutes  of  current  passed  would  indi- 
cate the  weight  of  the  coating.  At  this  time  the  tests  were  all 
carried  to  the  point  of  total  removal  of  the  coating. 

If  this  method  were  modified,  so  that  a  constant  amperage  were 
used,  and  the  specimen  removed  from  the  solution  from  time  to 
time,  say  every  half  minute,  and  the  test  stopped  when  failure  was 
first  noted,  the  thickness  of  coating  would  be  indicated  by  ampere 
minutes,  which  in  this  case  could  be  readily  noted  since  the  am- 
perage has  been  kept  constant.  In  order  to  insure  a  uniform  rate 
of  solution  for  all  parts  of  the  sample,  all  parts  of  the  specimen 
should  be  equally  distant  from  the  cathode.  If  the  shape  of  the 
object  prevents  this,  the  distance  should  be  made  great  enough,  by 
using  a  large  vessel,  so  as  to  make  the  variations  insignificant. 


GALVANIZING  SPECIFICATIONS  AND  TESTS  303 

Care  must  be  taken  to  use  a  voltage  lower  than  the  decomposition 
voltage  of  water. 

As  regards  the  Sherardized  coating,  the  disadvantage  of  this 
method  would  be  that  the  same  or  greater  weight  of  coating  would 
go  into  solution  per  ampere  minute  as  for  hot  galvanized.  As 
pointed  out,  this  is  not  the  case  with  the  Preece  test.  However, 
the  test  might  at  times  be  useful  for  a  laboratory  test  for  the  use 
of  the  Northern  Chemical  Engineering  Laboratories,  or  as  a  check 
method,  without  making  any  effort  to  bring  about  its  general  adop- 
tion as  a  commercial  control  method. 

Caustic  Soda  Test 

Another  test  for  a  zinc  coating  is  the  caustic  soda  test  as  supplied 
by  Professor  Walker.  This  test  will  show  the  presence  or  absence 
of  pores  or  cracks  in  zinc  coatings.  The  galvanized  article  is  sus- 
pended by  a  string  or  other  non-metallic  suspension  in  a  strong 
solution  of  caustic  soda  in  water,  heated  to  a  temperature  of  210 
dgs.  Fahr.  If  pin  holes  or  cracks  exist  in  the  surface,  bubbles  of 
hydrogen  will  be  observed  to  come  from  the  surface  of  the  article 
at  these  points,  while  if  no  pores  exist  no  hydrogen  will  be  evolved. 

After  considering  all  the  possible  methods  of  testing  protective 
coatings,  which  is  the  best  method  for  testing  Sherardized  material? 
The  best  one  is  that  which  can  be  successfully  used  on  a  commercial 
scale  by  a  $12  a  week  apprentice. 

Government  Galvanizing  Test 

In  using  this  test,  take  distilled  water  and  sulphate  of  copper, 
C.P.,  sufficient  to  make  a  saturated  solution  leaving  some  sulphate 
undissolved.  Solutions  to  be  used  at  a  temperature  of  60  deg  Fahr. 
Test  calls  for  one  minute  immersion  of  galvanized  work,  after  which 
the  work  is  rinsed  in  cold  water  and  dried,  and  again  immersed 
in  a  new  testing  solution  for  one  minute  and  again  \vashed  and 
dried  out  and  so  on  until  the  requisite  number  of  one-minute  dips 
have  been  made.  When  the  zinc  coating  breaks  down  and  shows  a 
deposit -of  bright  coppery  red  the  test  is  finished.  A  slight  appear- 
ance of  copper  does  not  necessarily  mean  that  the  zinc  coating  is 
entirely  broken  down,  but,  a  bright  red  deposit  must  show.  For 
some  characters  of  work  two  one-minute  tests  are  required  without 
the  galvanized  coating  breaking  down,  in  others  four  are  required. 

Professor  Burgess,  of  the  University  of  Wisconsin,  who  has  com- 


304 


GALVANIZING  AND  TINNING 


piled  very  interesting  data,  some  of  which  has  been  quoted,  has 
found  that  this  test  is  not  always  suitable  for  judging  the  thickness 
and  quality  of  electro-zincing.  For  testing  the  power  of  resistance 
of  the  coating  Professor  Burgess  has  made  use  of  diluted  sulphuric 
acid  and  has  found  that  an  electrically  deposited  coating  one-third 
the  weight  of  that  produced  by  the  hot  galvanizing  processes  has 
the  same  power  of  resistance  to  corrosion  as  the  latter  and  that  for 
a  coating  of  equal  thickness  the  proportion  of  resisting  power  is 
as  10  :1 

A  table  showing  the  time  of  deposit,  current  used  in  number  of 
amperes  and  the  resistance  to  successive  one-minute  immersions  as 
indicated  in  government  test  is  appended. 

Amperes  used 

per  sq.  ft. 

surface 

100 
90 
80 
70 
60 
50 
45 
40 
35 
30 
25 
20 
15 
10 

Salt  Spray  Test  for  Sherardizing 

Another  test  which  is  claimed  to  be  particularly  well  adapted  to 
making  comparisons  of  the  durability  of  metallic  coatings  applied 
by  processes  of  different  character  is  described  in  a  paper  read  by 
Mr.  J.  A.  Capp,  of  the  General  Electric  Company,  at  the  seven- 
teenth annual  meeting  of  the  American  Society  for  Testing  Ma- 
terials. 

There  are  several  processes  commercially  used  for  covering  the 
surfaces  of  metals  easily  corroded  or  rusted,  such  as  iron  in  its 
several  forms,  with  other  metals  less  easily  corroded,  or  with 
metallic  oxides.  These  may  well  be  called  "metallic"  protective 
coatings  in  distinction  from  the  types  of  coating  which  are  in  the 
nature  of  paints  or  their  equivalent. 

The  object  of  the  application  of  these  metallic  protective  coatings 


1st  test 

2nd  test 

2rd  test 

4th  test 

y6oz. 

1/3  OZ. 

y2oz. 

%  OZ. 

per  sq.  ft. 
Minutes 

per  sq.  ft. 
Minutes 

per  sq.  ft. 
Minutes 

per  sq.  ft. 
Minutes 

2% 

5 

7% 

10 

2% 

5% 

8 

11 

3 

6 

9 

12 

3% 

7 

ioy, 

14 

4 

8 

12 

16 

5 

10 

15 

20 

5% 

11 

16y3 

22 

6 

12% 

19 

25 

7 

14 

21 

28 

8 

161/2 

25 

33 

10 

20 

30 

40 

12V. 

25 

37  Va 

50 

161/2 

33 

50  ~ 

66 

25 

50 

75 

100 

GALVANIZING  SPECIFICATIONS  AND  TESTS  305 

is  to  enable  the  coated  articles  to  resist  atmospheric  exposure  with- 
out rusting  for  a  longer  time  than  they  could  withstand  such  ex- 
posure without  protection.  Obviously,  then,  the  only  final  test  of 
the  efficiency  of  a  given  type  of  coating  is  actual  exposure  to  the 
same  sort  of  influences  that  the  material  is  supposed  to  resist  in 
service.  If  the  coating  is  at  all  efficient,  this  takes  so  long  a  time 
that  more  rapid  methods  of  determining  relative  efficiencies  be- 
come a  necessity.  The  most  commonly  used  methods  of  testing 
such  metallic  protective  coatings  are  those  of  chemical  attack,  which 
in  effect  measure  either  the  thickness  or  the  weight  per  square  unit 
of  the  protective  coating.  Such  methods  of  chemical  attack  permit 
the  comparison  of  results  obtained  from  tests  upon  the  same  sort 
of  coating,  but  difficulty  is  encountered  when  attempt  is  made  to 
'  ompare  the  results  obtained  by  such  tests  on  one  sort  of  coating 
with  those  obtained  on  another  character  of  coating.  For  instance, 
the  well-known  Preece  test  yields  excellent  comparative  results  on 
galvanized  coatings.  When,  however,  it  is  used  for  coatings  ap- 
plied by  the  Sherardizing  process,  the  results  are  not  at  all  com- 
parable. Neither  is  the  Preece  test  applicable  to  coatings  of  tin  or 
of  lead.  In  the  case  of  Sherardized  articles,  it  has  been  suggested 
that  the  coat,  which  is  a  combined  structure  of  zinc  and  zinc  oxide, 
together  with  some  zinc-iron  alloy,  be  removed  in  strong  alkalies 
which  will  not  attack  the  iron  beneath.  This  would  enable  one  to 
determine  the  weight  of  coating  per  unit  of  surface  calculated  to 
metallic  zinc,  but  experience  has  shown  that  the  results  do  not 
necessarily  indicate  the  efficiency  of  the  coat,  and  that  it  is  not 
easy  to  determine  the  relative  proportions  of  zinc  and  zinc  oxide. 
Furthermore,  comparison  of  the  efficiency  of  a  Sherardized  coating 
with  ordinary  galvanizing  is  not  possible  when  the  Sherardized 
coating  is  tested  by  solution  in  a  caustic  alkali,  while  the  galvanized 
coating  is  subjected  to  the  Preece  test. 

Some  years  ago,  when  testing  electrical  insulation  such  as  is 
used  for  overhead  line  construction,  we  found  that  material  which 
stood  fairly  well  when  immersed  in  water  failed  badly  when  ex- 
posed to  the  weather,  especially  if  exposed  during  a  hard  rain. 
This  led  us  to  produce  a  rain  in  the  laboratory  by  sending  a  stream 
of  water  through  an  ordinary  rosette  such  as  is  used  with  a  garden- 
er's watering  can.  The  results  were  encouraging,  but  too  severe, 
because  the  individual  streams  played  steadily  on  one  spot  and 
produced  erosion.  Then  we  tried  an  atomizing  nozzle,  projecting 


306  GALVANIZING  AND  TINNING 

a  cloud  of  moisture  into  a  chamber  in  which  the  test  specimens  were 
exposed;  the  results  were  better,  but  there  was  still  a  possibility 
of  some  wear  if  the  article  was  directly  in  the  path  of  the  stream 
and  near  to  the  nozzle.  The  problem  seemed  to  be  solved  when 
care  was  taken  in  placing  the  articles  to  keep  them  out  of  the 
direct  path  of  the  jet  issuing  from  the  atomizing  nozzle.  As  ex- 
perience was  gained  with  this  type  of  test,  as  applied  to  insulating 
material,  it  was  found  that  what  seemed  to  be  the  essential  re- 
quirement was  the  maintaining  of  an  atmosphere  substantially 
saturated  with  moisture;  and  this  saturated-atmosphere  exposure 
has  been  one  of  the  tests  regularly  applied  to  all  insulating  ma- 
terials intended  for  outdoor  use  since  it  was  first  worked  out  some 
fifteen  years  ago.  It  has  been  found  to  give  reliable  indications 
of  the  ability  of  insulation  to  resist  weather,  except,  of  course,  as 
such  ability  is  affected  by  extremes  of  heat  and  cold,  erosion  from 
the  wind  carrying  dust  particles,  etc. 

The  problem  of  determining  the  resistance  of  protective  coatings 
to  weather  corrosion  is  very  similar  to  that  of  testing  insulations 
for  their  weathering  qualities.  The  conditions  of  exposure  are  the 
same,  and  hence  there  seemed  to  be  no  essential  reason  why  the 
saturated-atmosphere  test  would  not  apply  equally  well  to  pro- 
tective coatings  as  to  insulation.  Tests  were  begun  several  years 
ago  to  try  out  the  method,  and  the  only  fault  found  with  it  was 
that  it  was  somewhat  slow.  Good  coatings  did  not  show  any  signs 
of  breaking  down  after  several  weeks  of  continuous  exposure  to 
the  fog;  yet  there  Avas  encouragement  in  the  fact  that  bare  metal 
began  rusting  in  a  few  hours,  and  rust  spots  began  developing  on 
poorly  protected  surfaces  in  from  a  few  days  to  a  week. 

The  fact  that  more  trouble  is  experienced  with  trolley-line  sus- 
pensions along  the  seashore  than  with  the  same  devices  inland,  led 
immediately  to  the  trial  of  an  atmosphere  saturated  with  salt  water, 
with  astonishingly  satisfactory  results. 

As  now  used,  the  test  consists  in  exposing  the  Sherardized  ar- 
ticles in  a  copper-lined  box,  such  as  is  illustrated  in  Figs.  133  and 
134,  into  which  there  is  projected  by  compressed  air  an  atomized 
spray  of  2J  per  cent,  solution  of  NaCl  in  water.  Care  is  taken 
to  avoid  placing  the  test  specimens  directly  in  the  path  of  the  jet. 
To  insure  constant  saturation,  an 'excess  of  salt  is  kept  in  the  water 
at  the  bottom  of  the  chamber.  The  spray  is  produced  by  a  jet  of 
compressed  air  lifting  the  water  to  the  nozzle,  whence  it  is  pro- 


GALVANIZING  SPECIFICATIONS  AND  TESTS          307 

jected  as  a  cloud.  This  apparatus  is  of  the  common  atomizer 
type.  The  chamber  is  necessarily  not  tightly  sealed,  but  is  open 
sufficiently  to  permit  "breathing";  when  used  with  an  air  jet, 
there  is  a  slight  pressure  which  is  relieved  through  the  breathing 
openings.  If  desired,  the  test  may  be  modified  by  the  use  of  a 
fine  steam  jet  to  raise  the  temperature  of  the  atmosphere  in  the 
chamber.  The  specific  gravity  of  the  water  is  kept  at  1.026 
and  1.03  at  60  deg.  F.  There  is  also  the  possibility  of  render- 
ing the  test  atmosphere  slightly  acid  or  alkaline  by  suitable  addi- 
tions to  the  water  in  substitution  for  the  salt.  For  use  with  plain 
water,  the  closet  generally  used  for  cement  testing  does  very  well, 
provided  care  is  taken  that  it  is  so  arranged  as  to  maintain  the  air 
practically  at  100  per  cent,  relative  humidity.  When  using  salt 
solutions,  recourse  must  be  had  to  the  atomizing  jet  to  insure  the 
development  of  the  salt  fog. 


0  10  20  30  40  50  60  70  80  90  100 
Per  cent  Metallic  Zinc  in  Sherardizing  Dust 

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Salt  Spray  Test   Hours  /o  show  Rust  Evidence 
CHART  III.  RECORD  OF  COMPARATIVE  TESTS 

When  expose  1  as  described,  articles  have  a  very  thin  film  of 
moisture  over  their  surface,  but  there. should  be  very  few,  if  any, 
drops  of  sensible  size  on  the  objects.  Obviously,  the  test  is  very 
searching,  as  all  parts  of  the  surface  are  exposed,  and  any  pin  holes 
or  uncovered  areas  become  evident.  This  gives  one  an  opportunity 


308  GALVANIZING  AND  TINNING 

to  learn  something  of  the  efficiency  of  any  protecting  process  in 
taking  care  of  edges,  sharp  corners,  porous  spots  in  the  metal  sur- 
face, etc.  By  noting  the  character  of  the  general  final  breakdown, 
a  very  good  idea  of  the  evenness  of  the  coating  applied  may  be 
obtained. 

The  salt  spray  test,  as  it  is  called,  has  been  used  during  the 
last  four  or  five  years,  commercially,  by  the  General  Electric  Com- 
pany as  a  check  upon  the  products  of  its  process  of  Sherardizing. 
The  coated  articles  are  exposed  to  the  salt  fog,  and  are  exam- 
ined from  time  to  time  to  note  their  service  condition.  When 
the  coated  material  is  iron  in  any  of  its  several  forms,  red  dust 
begins  developing  as  soon  as  the  coat  breaks  down.  The  appear- 
ance of  red  dust  may  be  in  small  pin  points  which  gradually  ex- 
tend, or  it  may  appear  generally  over  the  surface  of  the  article. 
When  the  coating  is  relatively  thin  and  poor,  rust  may  develop  in 
from  two  to  three  hours  to  twenty-four  hours,  or  longer.  A 
better  coat  will  last  two  or  three  days,  but  a  well-applied  coat  of 
requisite  thickness  will  last  at  least  a  week.  If  no  rusting  is 
developed  in  this  time,  it  may  safely  be  assumed  that  the  life  of 
the  coating  will  be  practically  indefinite.  These  figures  are  based 
on  experience  with  both  Sherardizing  and  galvanizing. 

This  method  of  testing  Sherardized  articles  is  offered  in  replace- 
ment of  the  Preece  test.  Some  reasons  for  this  may  be  seen  by 
referring  to  Chart  III.  As  an  example,  we  may  take  a  sample 
with  a  deposit  of  .1377  oz.  per  square  foot  of  surface,  which  has 
stood  three  dips  in  the  Preece  test,  and  a  sample  with  .7  oz.  per 
square  foot  of  surface,  or  .5693  oz.  more,  which  stood  only  7  dips 
when  it  should  have  stood  11  or  12.  The  salt  spray  test  is  only 
an  exaggeration  of  what  may  be  expected  at  the  seashore  and 
differs  only  in  degree,  not  in  kind,  from  the  normal  conditions 
under  which  the  article  is  intended  to  be  used. 

Hydrochloric  Acid  and  Antimony  Chloride  Test  for  Sheets 
and  Wire 

Mr.  J.  A.  Aupperle,  metallurgical  engineer,  American  Rolling 
Mill  Company,  Middletown,  Ohio,  offers  a  new  method  for  testing 
the  spelter  coatings  of  sheets  and  wire  in  a  paper  read  before  the 
American  Society  for  Testing  Materials,  Atlantic  City,  N,  J., 
June  22,  1915. 

It  has  been  customary  to  express  the  weight  of  coating  on  wire 


GALVANIZING  SPECIFICATIONS  AND  TESTS 


30$ 


in  pounds  per  mile,  while  on  sheet  products  the  results  are  usually 
expressed  in  ounces  per  square  foot.  Obviously,  the  coating  on 
wire  expressed  in  pounds  per  mile  would  have  a  different  meaning 
for  each  gauge  of  wire.  If  the  results  are  expressed  in  ounces  per 
square  foot  of  surface  on  both  wire  and  sheets,  there  will  be  a  better 
understanding  as  to  the  thickness  of  coating  on  the  respective 
products.  In  stating  the  weight  of  coating  on  galvanized  sheets  it 
is  customary  to  express  the  weight  based  on  one  surface  only,  that 
is,  a  sheet  containing  2  oz.  of  coating  per  square  foot  really  contains 
1  oz.  on  each  side  of  the  sheet. 


FIG.   1.33.    SALT  SPRAY  TESTING  Box 

It  is  proposed  to  express  the  weight  of  coating  on  wire  in  ounces 
per  square  foot,  and  also  to  use  such  lengths  of  wire  that  the  num- 
ber of  grams  of  coating  found  will  be  equivalent  to  ounces  per 
square  foot,  without  calculation.  These  lengths  must  be  such  that 
the  surface  coated  is  equal  to  5.079  sq.  in.  It  is  likewise  proposed 
that  the  samples  for  determining  the  weight  of  coating  on  galvan- 
ized sheets  shall  be  2%  x  2*4  in.  (area  =  5.079  sq.  in.).  The 
number  of  grams  of  coating  on  a  section  of  this  size  will  also  express 
the  weight  of  coating  in  ounces  per  square  foot  without  calculation. 


310  GALVANIZING  AND  TINNING 

The  method  for  determining  the  weight  of  spelter  coating  consists 
of  using  a  small  amount  of  antimony  chloride  in  hydrochloric  acid 
(sp.  gr.  1.20).  Antimony  chloride  appears  to  hasten  the  solution 
of  the  coating,  and  after  the  coating  has  dissolved  a  thin  film  of 
antimony  plates  on  the  surface  of  the  base  metal  and  retards  the 
solution  of  iron  or  steel.  Experiments  have  shown  that  sheet  steel 
2'Vi  x  2*4  in.  which  loses  50  mg.  in  five  minutes  in  cold  hydrochloric 
acid  (sp.  gr.  1.20),  will  lose  in  that  time  only  1  mg.  in  the  same 
acid  containing  80  mg.  of  antimony  per  105  c.c.  of  acid. 

Determining  Spelter  Coating  of  Sheets 

In  the  proposed  method  the  metal  is  immersed  in  the  acid  only 
one  minute,  which  is  long  enough  to  dissolve  several  grams  of 
coating,  yet  the  amount  of  iron  or  steel  dissolved  is  negligible.  The 
small  amount  of  antimony  that  plates  on  the  surface  of  the  sample 
can  easily  be  removed  by  scrubbing  under  running  water.  This 
method  is  one  of  the  most  rapid  and  accurate  with  which  the  writer 
is  familiar,  and  a  determination  can  be  made  in  less  time  than  is 
occupied  in  making  the  Preece  test. 

For  determining  the  weight  of  coating  on  galvanized  sheets  cut 
several  samples  2%  x  214  in.  from  various  parts  of  the  sheet.  These 
samples,  about  five  in  number,  should  be  weighed  together  and  im- 
mersed singly  for  1  in.  in  100  c.c.  of  hydrochloric  acid  (sp.  gr. 
1.20),  to  which  has  been  added  5  c.c.  of  antimony  chloride  prepared 
by  dissolving  20  g.  of  antimony  trioxide  in  1,000  c.c.  of  hydro- 
chloric acid  (sp.  gr.  L20).  The  same  100  c.c.  of  hydrochloric  acid 
can  be  used  for  at  least  five  samples.  Five  cubic  centimeters  of  the 
antimony  chloride,  however,  should  be  added  for  each  sample  on 
account  of  the  antimony  being  removed  from  the  solution  by  the 
iron. 

The  samples  are  washed  and  scrubbed  under  running  water, 
dried  with  a  towel,  and  laid  in  a  warm  place  for  a  few  seconds. 
The  samples  are  again  weighed  together  and  the  number  of  grams 
lost  is  divided  by  the  number  of  samples  taken.  Each  gram  cor- 
responds to  1  oz.  of  coating  per  square  foot. 

Determining  Spelter  Coating  of  Wire 

A  small  section  of  the  galvanized  wire  should  be  stripped  in 
hydrochloric  acid  containing  antimony  chloride.  The  diameter 
of  the  black  wire  should  then  be  carefully  measured  in  order  to 


GALVANIZING  SPECIFICATIONS  AND  TESTS 


311 


determine  the  length  of  wire,  such  that  the  number  of  grams  of 
coating  will  represent  the  number  of  ounces  per  square  foot  of 
surface. 


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Cover  removed 


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FIG.    134.    DETAILS   OF   CONSTRUCTION  OF  SALT  SPRAY   TESTING   Box 


The  method  of  making  the  test  is  very  similar  to  that  outlined 
for  galvanized  sheets,  except  that  the  wire  is  first  cleaned  with 
carbon  tetrachloride  or  gasoline,  and  after  being  carefully  weighed 
is  placed  in  a  tall  glass  cylinder  containing  hydrochloric  acid  (sp. 
gr.  1.20),  to  which  has  been  added  from  2  to  3  c.c.  of  antimony- 
chloride  solution  of  the  same  strength  as  used  on  galvanized  sheets. 
The  reason  for  using  one-half  the  amount  of  antimony  chloride 


312  GALVANIZING  AND  TINNING 

in  the  case  of  wire  is  on  account  of  taking  one-half  the  area.  As 
previously  stated,  the  coating  on  galvanized  sheets  is  expressed  in 
ounces  per  square  foot,  considering  one  side  only,  when  in  reality 
this  amount  of  coating  represents  2  sq.  ft.  of  surface.  After  im- 
mersing the  entire  length  of  wire  for  1  min.  it  will  be  found  con- 
venient to  pour  the  acid  solution  into  another  tall  cylinder  in  order 
to  facilitate  removing  the  wire.  The  wire  is  then  scrubbed  under 
running  water,  wiped,  thoroughly  dried  in  a  warm  place  for  a  few 
seconds  and  again  weighed.  Each  gram  lost  corresponds  to  1  oz. 
of  coating  per  square  foot.  For  direct  comparison  with  the  weight 
of  coating  as  expressed  on  galvanized  sheets,  this  figure  should  be 
doubled. 


INDEX 


Acetate,  Sodium,  in  Elec.-Galv. 

solution  221 

Acid  consumption  in  pickling..     46 

Hydrofluoric    43 

Hydrofluoric  pickle   212 

in    porous   castings   effect   in 

Sher  279 

Muriatic  43 

Muriatic,  pickle   211 

Nitric,  pickle  21i 

Preventing  waste  of  280 

Sulphuric  in  Elec.-Galv.  solu- 
Sulphuric  in  Elec.-Galv.  solu- 
tion   219.  220,  221 

Sulphuric,  pickle   211 

tanks,   Construction  of 3( 

Tartaric,  in  Elec.-Galv.  solu- 
tion   22J 

Action  of  gas  in  m^tal 220 

Agents    for    improving     Elec.- 
Galv.  solutions   22 

Agitation    of     solution     Elec.- 
Galv 153 

Air  pressure  in  Schoop  process  102 
trapped  in  tubes,  Prevention 

of    .. 194 

Alcohol,  Its  effect  on  Elec.-Galv. 

bath  222 

Alum,     Effect    on      Elec.-Galv. 

bath  222 

Aluminum    43 

Chloride,     Sodium     in    Elec.- 
Galv.  solution   221 

coating  by  Schoop  process....  96 
improves  appearance  of  work  43 
Sulphate  of,  in  Elec.-Galv. 

solution 218,  220,  221,  222 

Ammonia  absorbed  by  charcoal  229 
Ammonium    chloride    in    Elec.- 
Galv.  solution  218,  219,  220,  221 
chloride,  Zinc,  Substitute  for 

sal   ammoniac   42 

Amperage  for  Elec.-Galv. 

153,  218,  219 
required  under  different  con- 


ditions 


207 


Analysis   of   zinc   dust 274 

Anchors,  Ashler  Hot  Galvanized  11 

cleaned  by  sand  blast 59 

Angles,    Castings    with     sharp 
angles,  require  special  pre- 
paration   133 


Annealing     action      in      Sher. 

furnace  277 

Anodes  149,  189,  199,  203,  222 

Automatic   removal   of 164 

Choice  of  207 

Cleaning  scum  from  164 

Special     shapes     for    depres- 
sions    223 

Wrapping,  to  galv.  inside  of 

tubes  without  contact 193 

Antimony  chloride  and    hydro- 
chloric acid  test  308 

Apperance   of    work    improved 

by  aluminum  43 

Applying  zinc  coating  by  Elec- 

Galv.  process  222 

Ash  can  for  zinc  dust 233 

cans,  Temp,  for  Hot  Galv.  of     68 

pit  17,     25 

Ashler  anchors,  Hot  Galv 11 

Ashes,    Zinc,    How    formed 90 

Asphalt  lined  tanks  208 

Asphaltum,  Use  of,  in  tank  con- 
struction      31 

B 

Band  iron,  Formula  for  Elec.- 
Galv.  of  218 

Schulte     machine    for    Elec.- 
Galv 204 

Bars     for     Potthoff     machine, 

Elec.-Galv 191 

Barrel,  Dry  tumbling,  Loading 

of  52 

Unit  for  Elec.-Galv.  a  modi- 
fied form  181 

Unit  for   Elec.-Galv.,   Opera- 
tion    181 

Barrels,  Elec.-Galv. 

Cleaning,  rinsing  and  plating 

unit  177 

Daniel's  hand  and  lever 165 

Ele-Kem   automatic  174 

Potthoff's   automatic   168 

Schulte's  mechancial  172 

Unloading  automatically.. 168-173 
Barrels,  Sand  blast 

Details  of  construction 63 

Operation  of  61 

Barrels,  Tumbling 

Charging  of 54,  213 

Construction  of    53 

Detailed  plan  of  53 


INDEX 


Barrels,  Tumbling 

Elevation   of   5 

Loading   of    5 

Basins   Catch  under    acid    and 

water  tanks  1 

Baskets   31,  11 

for    tinning    small     articles, 

Construction  of  11 

Bath,   Hot   alkali,   for  cleaning 
gray      iron     castings      for 

tinning 13 

showing  acid  reaction  the  best21 
Baths,  Cleaning  and  pickling..21i 
Bayliss  process  for  Hot  Galv- 

sheets   , 7i 

Beams,     Steel     grillage,      Hot 

Galv II 

Benzoic  acid,  its  effect  on  Elec.- 

Galv.  bath   222 

Black  pickling 46 

spots,  Eliminating,  from  fin- 
ished work  279 

spots      on      Sher.       articles, 

Cause   of   279 

Blue  dust,  Advantages  of 257 

Metallic  content  267 

Takes  longer  to  cool 

"Blue  powder" — zinc  dust....  25( 
Boiling  out  kettles,   Tools   for     93 
"Boiling"  the  tin  in  re-tinn- 
ing    12 

Bolts,   Allowance   for  thickness 

of  coating  in  Sher 268 

Equipment  for  Sherardizing  233 
Boric   acid  in   Elec.-Galv.   solu- 
tion   218,  219,  220 

Box,  Testing,  for  salt  spray 

309,  311 

Boyles  and  Charles,  Law  of....  229 
Bricking  in  a  small  galv.  kettle     20 
Brickwork  on  galvanizing  kettle 
without  grates  and  having 

one   draft  hole   26 

Bronze,    Depositing    on      Sher. 

articles  282 

Brushing,  Objection  to,  in  test- 
ing Sher 298 

Scratch   211 

surplus   zinc   from   article....     70 

Buffing  Sher.  articles 282 

Burnishing  barrel,  Ele-Kem....  175 

Sher.  articles  282 

By-products  of  Hot  Galv.  pro- 
cess         84 

of     Hot    Galv.    process,    Re- 
covery       85 

C 

Cable  or  chain    conveyer     ma- 
chine, Fleischer's  161 

strip,     armored,      Test      for 
thickness  of  zinc  coating..  226 


Car,  Transfer,  Construction  of  253 
Cartridge  steel,  Elec.-Galv.  of  194 

Casing    for    draft   holes 24 

Castings,  Avoid   sharp   angles  133 
Cast-iron,  Preparing  for  tum- 
bling       54 

Cleaning  210 

Drying,  Arrangement  for....     26 

Elec.-Galv.   solution   for 219 

for  grate  fired  Galv.  kettle..     23 

for  small  Galv.  kettle  21,  22 

for  tinning  kettle 116 

Gray  iron,  Cleaning  with  hot 

alkali  bath  135 

Gray  iron,   Heat  required  in 

tinning  142 

Gray  iron,  Preparing  for  tin- 
ning    133 

Gray    iron,     Removing     sand 

from  133 

Gray    iron,    Removing     sand 

with  hydrofluoric  acid 134 

Gray  iron,  Time  required  to 

tin   141 

Gray  iron,  Tinned  for  electro 

plating   136 

Gray  iron,  Tinning  of 129 

Handling  delicate  ones  in  roll- 
ing barrel  57 

Malleable     and     gray     iron, 

Pickling   of   263 

Method     of     immersing      in 

roughing  kettle   140 

Over-pickled,  Remedy  for  ....135 
Sandy,  Cleaning  with  hydro- 
fluoric acid  113 

Sandy,  Cleaning  with  sul- 
phuric acid  49,  112 

Sandy    gray    iron,     Cleaning 

with   sand  blast 135 

Sandy  gray  iron,  Cleaning 
with  sulphuric  acid  for  tin- 
ning   135 

Solution  for  finishing  when 
work  is  not  thoroughly 

cleaned 55 

Storing  after  tumbling 57 

Testing  to   see    if    they    are 

properly  cleaned  55 

Time  required  to  clean  in 
tumbling  barrel  and  sand 

blast  55,  59 

Time   and   speed   required   to 

clean    in    tumbling   barrel     55 
ast    iron,    Preparing   for   tin- 
ning   54,  133 

atch  basins    under    acid    and 

water  tanks  15 

austic-soda  solution  210 

austic-soda  test  293,  303 

eiling,    High,    for    plants 14 


INDEX 


315 


Cement  floor,  Advantage  of 233 

Chain   or   cable    conveyer    ma- 
chine, Fleischer's  161 

conveyer     machine,    Miller's, 

Construction  of  153 

conveyer  machine,  Miller's  ..  156 
Equipment  for  Sherardizing  233 
Grips,  Removing  scale  from  211 
Cleaning,  in  dry  tumbling 

barrel   53 

Chamber  pails,  Temp,  for  Hot 

Galv.   of  

Charcoal,    Absorption    of    am- 
monia    229 

Charging  of  tumbling  barrel 

54,  213 

Charles  and  Boyles,  Law  of....  229 
Chart,    Deposit    and    temp,    in 

Sher 270 

Chilled   shot    used    instead    of 

sand  in  sand   blasting 64 

Chimney   construction   for   Hot 

Galv.    plant   ...; 17 

Chloride,  Ammonium,  in  Elec.- 
Galv.  solution,  218,  219,  220,  221 
of    ammonia     in     Elec.-Galv. 

solution 218,  219,  220,  221 

•    Sodium,  Aluminum  in   Elec.- 
Galv.  solution  221 

of    zinc    in    Elec.-Galv.    solu- 
tion  218,   219,   220,   221 

Cinder  test  for  Galv.  coating  225 
Citrate,   Sodium,  in   Elec.  Galv. 

solution  221 

Cleaning  barrel  51,  174,  177 

castings     with    sulphuric    or 

hydrofluoric  acid  49 

Electro   215 

equipment  149 

most   essential    step    in    Sher-     . 

ardizing   232 

old  galvanized  work  146 

old  tinned  work  146 

Potash  solution  for 196 

Rinsing    and    plating    units, 

168,  172,  177 
Rinsing     and     plating    barrel 

unit,  A  modified  form 182 

scum   from    anodes 164 

Sher,   articles   280 

Spec,  for 287 

Tanks    208 

work  for  Elec.-Galv 209 

Cloth,  Wire,  Formula  for  Elec.- 
Galv.   of   218 

King's     machine     for     Elec.- 
Galv 194 

Root's     machine     for    Elec.- 
Galv 202 

Coal  hods,  Temp  for  Hot  Galv.     68 
Time  required  to  Hot  Galv.    70 


Coal,  Pea,  Cost  of,  in  Sher.  one 

ton  285 

Coating,      Spelter     of     Sheets, 

Determining  310 

Zinc,  Applying  in  Elec.-Galv. 

Process  222 

Zinc,  Locating  cracks  in 294 

Zinc,  Non-uniformity  in  Sher. 

Remedy  for  279 

Coke  43 

Burning,  Sher.  furnaces  234-240 
Cost  of  in  Sher.,  one  ton....  285 
Dust,  Use  of,  in  Hot  Galv. 

wire,  etc 77 

Foundry  unsatisfactory  43 

Gas  gives  best  results 43 

Cold  or  Elec.-Galv 148,  226 

Colloids  222 

Coloring     and     finishing    Sher. 

articles   282 

Combination  formula  for  clean- 
ing and  plating  216 

Combustion    chambers     in     gas 

and  oil  burning  furnaces  241 
in    coke    burning    Sher.    fur- 
nace    234 

in  Sher.  furnace  238 

Conductors,    Copper    149 

Rule  for  figuring  size  of 207 

Construction     of     three    drum 
coke  burning  Sher.  furnace 

234 
Cooling  and  unloading  drums  276 

Drums    271 

Frame   233,  255 

Hot  Galv.  work  70 

Out  276 

platform   247,  248 

Rapid,   Effect  of  275 

Slow,    better     than     fast     in 

Sher 273 

Coping  plates 25 

Copper  acid  solution  225 

Bath   198 

Cyanide  bath  225 

Cyanide  bath,  action  of 212 

Cyanide   strike   211 

Depositing,  on  Sher.  article  282 

Dip.    Formula   for 212 

Flashing  211 

Sulphate  or  Preece  test 

290,  294,  301 
Correct   position    of   pyrometer 

in  kettle  35 

Corrosion   of    iron     and    steel, 

Prevention  of   9 

Theory   of    11 

Corset  steel  Elec.-Galv.  of,  194,  225 
Cost  of  Elec.-  and  Hot  Galv..  224 
of  coating  with  zinc  by  Schoop 
process 102 


316 


INDEX 


Cost  of  coke  in  Sher.  one  ton  285 

of  elec.  current  224 

of  Elec.-Galv 208,  224 

of  illuminating  gas  in  Sher..  285 
of  metal  spraying  with  "pis- 
tol"      105 

of  oil  284 

of     producer     gas    in    Sher. 

one    ton    285 

of  production  (all  processes)     72 

of  Sher.  per  ton  284 

of  zinc   dust   284 

Cowper-Cowles  Sherard,  In- 
ventor of  Sherardizing  pro- 
cess    227 

Cracks,  Locating  in  zinc  coating294 

Cyanide,  Copper  bath 225 

fumes,  Removal  of  150 

Cyclone  metal  spraying  device, 

Operation  of  98 

D 
Dairy     utensils,     Coating,     by 

Schoop  process  104 

Daniel's  Elec.-Galv.  barrel 165 

Screw  conveyer  machine  158 

Davies'  method  of  Galv.  sheets 

74 
Defective     coating      frequently 

due  to  poor  cleaning 209 

Density  of  Elec.-Galv.  solutions  219 

Deposit,  Heavy  in   Sher 275 

Deposition,  Double  223 

Dextrine  in  Elec.-Galv.  solu- 
tion    220 

Effect     of,     on      Elec.-Galv. 

bath  222 

Dip,  Formula  for  copper 212 

Dipping  gray  iron  castings   in 

tin 138 

in  molten  zinc,  Time  requir- 
ed      69 

Preparing  cleaned  work  for     64 

work  in  molten  zinc 69 

Dont's  in  Sher.  practice 278 

Double  deposition  223 

Drainage  of   Hot   Galv.   plant     15 

of  tinning  plant  109,   130 

Drier,  Front  section  of 27 

grate  and  firebox,  Detail  of     30 

Operation  of  65 

Placing  work  in  it  to  keep  hot 

without  burning  acid  off.—     65 
Plan  and  details  of  construc- 
tion       28 

Plan  and  elevation  of 29 

Plates  covering  fires  will  do 
for   small   lots   of  work....     65 

Proper  location  of 65 

Dross,  Hard  zinc  84 

Kept   from  coming  in   direct 
contact     with     bottom    of 


kettle  by  6  or  8  in.  layer  of 

lead    66 

on   re-tinned   article,   Method 

of  preventing  125 

Remelting    145 

Removal     of,     from    tinning 

kettle  141 

scoop,  Construction  of 33 

Storage  of  145 

Value  of  145 

Zinc,  How  formed  85 

Zinc,  Method  of  recovering..     85 
Zinc,   sweating,   Temperature 

and  operation  88 

Drums,   Cooling   271 

Cooling   and   unloading   276 

Loading  261,  263,  266 

Loading  into  furnace 254 

Rotation  of,  in  Sher.  furnace 

237,  267,  273 

Sherardizing  233,  250,  251 

Sherardizing,  Construction  of250 
Sher.       Cylinder,       fastening 

heads  on  251 

Sher.,   Square   250 

Dry  Galv.  or  Sherardizing  227-286 

tumbling  52,  209 

Tumbling  of   wire   work 213 

Drying  apparatus  27,  65,  200 

Barrel  Ele-Kem  176 

Castings,  Arrangement  for..     26 

Hot  Galv.  work  71 

plate 17 

work      after     tumbling    and 

sand  blasting  65 

of  heats  in  Sher 267 

Duration  of  Elec.-Galv 225 

Dust  screening  machine 

233,  251,  276 
Dynamo  206 

E 

'Edis  Compound,"  A  substitute 
for  sulphuric  acid    in    dry 

cakes  48 

Egg  beaters,  Tinning  of 129 

Electric     current,     Chart     for 

Sher 271 

Hoist  for  Sherardizing  plant  234 
Electrical  condition  accompany- 
ing evolution  of  gases 230 

equipment  206 

installation  150 

lectrically    heated    Sher.    fur- 
nace    248 

Electro-cleaner,   Action   of 212 

Electro-cleaning  215 

Cleaning  solution  211 

Elec.-Galv.,    Advantages    of—.    148 
Barrel    Unit    with     Cleaning 
and  Rinsing  tanks  177 


INDEX 


317 


Elec.-Galv.  Apparatus 

Daniel's  Screw  conveyer 158 

Fleischer's    Cable     or     Chain 

Conveyer  161 

Hanson  &  Van  Winkle's  Pipe 

and  Tube  189 

King's  Continuous  Wire  Cloth 

194 

Meaker   Continuous  type 184 

Miller's  Chain  Conveyer 153 

Potthoff's  Tube  191 

Root's  Wire  Cloth  202 

Schulte's   Wire  204 

Elec.-Galv.  Barrels 

Cleaning,   rinsing    and    plat- 
ing unit  177-182 

Daniel's  hand  and  lever 165 

Ele-Kem  automatic  174 

Potthoff's  automatic 168 

Schulte's  mechanical  172 

Elec.-Galv.  or  cold  process..!48-226 

Cost  of   208,   224 

Duration  of  225 

Earliest  record  of  148 

Heavy  deposit  223 

Elec.-Galv   of  corset  steels 225 

Open  tank  work .....153-165 

Plant,  Layout  of 150 

Plant,  Removing  fumes  150 

Preparing  work  for 209 

Solution  for  castings   219 

Solution  for  soft  deposit 220 

Solution  for  testing  287 

Solutions  217-222 

Solutions,  Agents  for  improv- 
ing    222 

Solutions  for  barrel  plating  219 

Spongy  deposit  223 

Tests,  Table  of  304 

Time  required,  218,  219,  222,  223 
vs.     Hot     Galv.    comparative 
costs  224 

Electro  plating,  Gray  iron  cast- 
ings tinned  for 136 

Electrolytic  test 302 

Elec.-Galv.  barrel  saw-toothed 
construction  174 

Elevation   of    re-tinning    plant 
containing  four  kettles....   122 

"Embalming,"      or     protecting 
iron  from  rust  9 

Emery,  Use  of  in  tumbling....  218 

Epsom      salts      in      Elec.-Galv. 
bath  220 

Equipment   and  plant   for   Hot 

Galvanizing  14,  17 

Electrical  206 

for  Elec.-Galv.  plant  149 

and  location  of   Sher.  plant  233 

Erlenmeyer  flask,  Use  of 258 

Exhaust  for  dust  screener 252 


Fats  will  redeposit  in  Sher 281 

Filling  a  new  kettle 66 

Finishing    and     coloring     Sher. 

articles   282 

of  re-tinned  work  127 

Firing  a  new  kettle 67 

Flaking,  Cause  of  in  Sher 281 

Flashing  Copper  211 

Flat    stock,     Loading    in     Sher. 

drum  265 

Fleischer's  Cable  or  Chain  con- 
veyer Machine   161 

Floor  Cement,  Advantage  of 233 

Floor  space  required  for  Sher. 
plant  of  one  ton  capacity  233 

Flues,  Arrangement  of  28 

Underground  17 

Flux  boxes  on    Hot    Galv.    Ma- 
chines         74 

Exercise  care  in  removing....     89 

formed  by  sal  ammoniac 42 

for  tinning  kettle  in  coating 

cast  iron  139 

"Flux  guard"  70 

in  kettle    73 

prevents  zinc  from  oxidizing     69 
Thick  or  lumpy,  To  remedy  139 
Food    choppers,   Time   required 

for  sand  blasting  59 

Forgings,  Pickling  48 

Formula  for  cleaning  and  plat- 
ing   216 

for  copper  dip  212 

for   Elec.-Galv.   solutions  ....  218 
Foundation  washer,  Cast  iron     25 

Frames,  Cooling  233,  255 

Loading   233 

Fuel  for  tinning  107 

Proper  depth  in  firebox 67 

Fumes  217 

carried  off  by    exhaust    sys- 
tem      150 

a  menace  to  machinery 14 

Furnace,  Gas,  single  drum 240 

Sherardizing  233 

Sher.     Coke     burning,     Elev. 

and  details  of  single  drum  238 
Sher.     Coke     burning,     Elev. 
and  details  of  three  drum  235 

Sher.  electrically  heated 248 

Sher.    Elec.     heated,     Opera- 
tion of  271 

Sher.  for  long  job  work 244 

Sher.    Gas   and   oil   burning 

239,  248 
Sher.,   Loading   drums   into   254 

G 

Galvanic  action    taken    up    by 
zinc    ..  12 


318 


INDEX 


Galvanized  work,  old,  Cleaning 

of  146 

Galvanizing,  kettles  allowed  to 

cool  off  not  economical 13 

Sheets,  Construction  of  ma- 
chines for  74,  75 

Sheets,  Heathfield  method....     75 
Sheets,     Three     process     de- 
scribed      12 

Specifications  287 

Test,  Government 303 

Gas,  Action  of,  in  metals 229 

Gas  and  oil  burning  Sher.  fur- 
naces     239-243 

Bubbles  in  Elec.-Galv.  Pre- 
vention of  203 

Contents  of  metals   228 

Illuminating,     Cost      of,     in 

Sher 285 

Pressure  of  in  Schoop  pistol  101 

Producer,  Cost  of  in  Sher....  285 

Gelatine,  Use  of  in  Elec.-Galv  222 

Generator,  Location  of 207 

Low  voltage   149 

Girders,    Coating     by     Schoop 

process  104 

Glucose,    Effect    on    Elec.-Galv. 

bath  222 

Glue,      Effect     on      Elec.-Galv. 

bath  222 

Glycerine 43 

Action  of,  in  kettle 69 

in  Elec.-Galv.   solution.... 220 

Use  of  in  making  flux  foam 

up  70 

Grape  sugar  in  Elec.-Galv.  solu- 
tion   218,  221 

Grasselli  dust  256 

Dust,   Advantages    of 257 

Dust,  Metallic  content 267 

Grate  and  firebox  for  drier,  De- 
tails of  30 

and  firebox  for  tinning  kettle 

131 
bars,   Method   of    setting    in 

tinning  kettle 116 

fired  galvanizing  kettle,  De- 
tails of  construction 23 

Grates 24,     25 

Gray  iron   and  malleable  cast- 
ings, Pickling  of 263 

iron  castings,   Preparing  for 

tinning  133 

iron  castings,  Proper  tem- 
perature for  Hot  Galvan- 
izing    68 

iron  castings,  Removing  sand 

from  133 

iron  castings,  Removing  sand 

with  hydrofluoric  acid 134 

Grease  or  oil,  Removal  of 210 


Grease  or  oil,  Removal  of  from 

stamped  ware  122 

Removing   from   work   to   be 

tinned  114 

Grillage     beams,      steel,      Hot 

Galv 10 

Grinding  and  scouring  machine 

213 
Grit,   Diamond,   Advantage  of     64 

Use  of  in  wet  tumbling 213 

used  instead  of  sand  in  sand 

blasting   64 

Gum  tragacanth  in  Elec.-Galv. 
solution  221 

H 

Handling  pickled  work  48 

Hanson   &    Van     Winkle    Pipe 

and  Tube  Galv.  Machine..  189 
Hardware   Saddlery,    Time    re- 
quired  to    clean    by    sand 

blast  59 

Saddlery,  Tinning  of  109 

Testing  samples  288 

Heathfield's    method    for    Galv. 

sheets   75 

Heathfield     Process,     Zinc    de- 
posited on  sheets  by 76 

Heat  Controlling  in  Sher.  fur- 
nace    238 

Heating  kettles  147 

Heats,  Duration  of  in  Sher....  267 
Heavy    deposit    in    Elec.-Galv. 

process   1 223 

Hoist,  Electric  280 

Electric,      for      Sherardizing 

plant  234 

Hood,  Exhaust,  for    dust    sep- 
arating machine    252 

Hoods  for     kettles    and    tanks, 

size  of  15 

for  kettles,  Movable  14 

Hoop  iron,  Elec.-Galv.  of 194 

Hot  Galv.  automatically  74,  76,  77 

Dipping  the  work  69 

Equipment  17 

Laws  of  physics  applying  to     18 

Plant   and   equipment 14 

Plant,  Floor  plan  of 15,     16 

Plant,  small  17 

Plant,  steam  required  15 

Plant,   Ventilation   of 14 

Plants,  Drainage  of 15 

Room   fittings 14 

Solution  for  testing  287 

Tools,    Construction   of 32 

Tools  for    31 

Work,  Cooling  after  dipping     70 

Hot  rolled  steel,  Cleaning 209 

Hydrochloric  acid  and  antimony 
test  ...,          308 


INDEX 


319 


Hydrofluoric  acid  43 

best  for  removing  sand  from 

gray   iron  castings 134 

Cleaning  sandy  castings  with 

113 

Pickle  212 

Pickle,  Test  of  263 

Tanks   for    16 

Use  of  in  cleaning  castings     49 
Hydrogen  absorbed  by  pladium  229 
Hydrogen  gas  causes  damage     80 
Remedying  damage  caused  by 

80 
I 

Ice  cream  freezers,  Tinning  of  129 
Impurities  lower  melting  point  36 
Inspection  of  material  before 

Sher : 279 

Ions,  Free,  Effect    on    precipit- 
ation of  vapor 230 

Iron     and     steel,     Comparative 
value     for     making     Galv. 

kettles  20 

Corrosion,  Prevention  of 9 

Iron  Band,  Elec.-Galv.  of 204 

Formula   for   Elec.-Galv.   of  218 
Iron,  Cast,  Preparing    for    tin- 
ning    54,  133 

Iron,    Determining    amount    of 

in  Galv.  coating    292 

Malleable  and  gray,  Pickling 

of  263 

Proper  grade  for  making  Hot 

Galv.  kettles  18 

Sulphate   in   Elec.Galv.   Solu- 
tion      221 

Wrought   and    steel,    soluble 

value  of  18 

Zinc  Alloy  227 


Japanning,  Sher.  articles 282 

K 

Kettles,  boiling  out,  Tools  for     93 
Burst  by    allowing    them    to 
cool  with  quantity    of    zinc 

dross  in  them 86 

Filling  new  66 

for  molten  zinc  16 

for     recovering     zinc     dross, 

Construction  of  87 

for  refinishing  old  galvanized 

and  tinned  work  147 

for  retinning  121 

for  tinning   109 

for   tinning    gray   iron   cast- 
ings, Arrangement  of  grate 

bars  and  ash  pits  131 

for  tinning  gray    iron    cast- 
tings,  Elevation  of., „...  131 


Kettles  for  tinning    gray    iron 

castings,  Size  and  shape 144 

for  tinning  spoons,  etc.,  Size 

of 119 

for  tinning  wire  119 

Galvanizing,   allowed   to   cool 

off  not  economical  13 

Galvanizing,  Bricking  in 20 

Galvanizing,  Castings  for....     21 
Galvanizing,  grate  fired,  cast- 
ings for  23 

Galvanizing,  grate  fired,  Con- 
struction of  23 

Galvanizing,  grate,  fired,  plan 

and  elevation  22 

Galvanizing,   One   piece   25 

Galvanizing,  Selection  of 20 

Galvanizing,     Setting    small, 

without  ash  pit 20 

Galvanizing    without    grates, 
one    drafthole,     Plan     and 

elevations  26 

Galvanizing,     Heating     sides 

and  bottoms  of  147 

Galvanizing,    Leaks    in    new 

or  old   92 

Galvanizing,  Life  of  92 

Galvanizing  Listing,  Use  of  126 
Galvanizing,  New,  Firing  ....  67 
Galvanizing,  New  often 

ruined  by  improper  filling     66 
Galvanizing,     New,     Packing 

slabs  of  spelter  in 66 

Galvanizing,    Pi-eparing,    be- 
fore starting  to  dip 69 

Galvanizing,  Replacing  old..     92 

Re-tinning,  Replacing  128 

Roughing  140 

Galvanizing,      Selection       of 

best  material  for  making     18 
"Skinning"  for  removing  sur- 
plus  tin   in   re-tinning 127 

Soaking  121 

Tinning,  Castings  for 116 

Tinning,    Materials    used    in 

constructing  144 

Tinning,   Plan   and   elevation 

of  115 

King    Continuous    Wire     Cloth 

Machine   194 

"Kleanrite,"  a  substitute  for 
sulphuric  acid  in  powdered 
form  ..  48 


Labor  cost  in  Sher 284 

in  Sher.  Improving  280 

Skilled  more  reliable  than  py- 
rometer on  miscellaneous 
work  34 


320 


INDEX 


Labor,    Unskilled   expensive   in 

Hot    Galv 13 

Lacquer  finish  on  Sher.  articles  283 
Laundry  machinery,  Coating  by 

Schoop  process  104 

Law  of  Boyles  and  Charles 229 

Lead  Acetate  and  Preece  Tests 

Compared  301 

Lead  acetate  test  291,  299 

acetate  Test,  Advantages  of  301 

Lead  as  cushion  for  dross 66 

lined  tank   208 

lining  in  Tanks  31 

not  electro  positive 12 

Pig    42 

Leaking  prevented    in    articles 

by  tinning  before  plating  129 
Leaks  in  kettles,  Repairing....  92 
Licorice,  Its  effect  on  Elec.- 

Galv.  bath  222 

Lime     solution      to      neutralize 

acid  262 

Lining  tanks  with  sheet  lead..     31 

Listing  kettle,   Use   of 126 

Loading  drums  261,  263,  266 

Frame  233 

Platform  246 

wet  tumbling  barrel 54 

Location     and     equipment     of 
Sher.  plant  233 

M 
Machinery  Used  in  Hot  Galv., 

Composition  of  18 

Magnetic      oxide,     Removal     of 

from  bath  210 

Malleable    iron    castings,    Tem- 
perature  for    Hot   Galv....     68 

iron  casting,   Tinning  of 106 

Materials  used  in  Hot  Galv....     41 

used  in  Sher 256 

Vapor  tension  of  230 

Meaker     Continuous     Machine, 

Operation  of  188 

Continuous    Type    Elec.-Galv. 

Machine  184 

Mechancial    Elec.-Galv.    appar- 
atus    153 

•"Melting  out" 67 

Melting  point    lowered    by    im- 
purities       36 

Melting  point  of  zinc 35 

Metal,  Action  of  gas  in 229 

Powdered,  Use    of    in    metal 

spraying  96 

Metallic  method  of  rust  preven- 
tion          9 

Metallic  zinc  in  zinc  dust,  Meth- 
ods  for   determining 258 

Metals    are    extremely   porous  223 
Gas  contents  of  228 


Metals,  Spraying,  Position  of 
apparatus  in  applying  coat- 
ing    103 

Spray  Process,  Schoop 94 

Methods      of     producing     zinc 

vapor  230 

Miller  Chain  Conveyer  Ma- 
chine, Construction  of 153 

Chain  Conveyer  Machine,  Op- 
eration of  156 

Mill  scale,  Removal  of 210 

Moist  air  test  226 

Molasses,  Its  effect  on  Elec.- 
Galv.  bath 222 

Morf  patent  for  spraying  pistol  95 

Motion  during  Sher 273 

Muriatic  acid 43 

A  "safe"  pickle  49 

Dip  for  a  flux  64 

Formula  for  a  quick  pickle     50 
Mixture  for  cleaning  castings 

in  tumbling  barrel 55 

Pickle   211 

Removing  scale  or  rust  with 

48,  113 
N 

Nails,  Equipment  for  Sher 233 

Sher.  test  of  298 

Temperature    for    Hot    Galv. 

of  68 

"Nesting"  of  articles  prevented 

122 
Netting,  Wire,  Hot  Galv.  of..     77 

Nickel  solution  225 

Nitric  acid  pickle  211 

Non-metallic    method    of    rust 

prevention   9 

Nuts,  Testing  coating  of 289 

O 

Oil   43 

and   gas   burning    Sher.   fur- 
naces  239,  248 

Fuel,   Cost  of  in   Sher 284 

Mineral  lard,  best 43 

or  Grease,  Removal  of 210 

Removing  in  Sher 281 

Old   work   quickly    cleaned    by 

sand  blast   59 

One   piece   galvanizing  kettle..     25 

Open    tank    Elec.-Galv 153,    165 

Operating  costs  in  Elec.-Galv.  224 
Operation    of    chain    conveyer 

plating  machine  156 

of  elec.  heated  Sher.  furnace  271 
of    Meaker    continuous    type 

Elec.-Galv.  machine 188 

of  King's  wire  cloth  machine  196 

of  plating  barrel  unit 181 

of     screw    conveyer    plating 
machine  ..   160 


Wattaee  G.Imhoff 


INDEX 


321 


Overheating  destroys  kettle 37 

in  tinning,  Effect  of 144 

Oyer  pickling  45,  47,  212 

Remedy  for  135 

Oxide,     Magnetic     Removal     of 

from   bath   210 

of  Zinc,  Value  of  in  Sher....  231 
Oxygen      absorbed    by    spongy 

platinum    229 

P 

Packing  Elec.  heated  Sher.  fur- 
nace    266 

Paint,  Old,  Removal  of  by  tum- 
bling       53 

Removing  from  work    to    be 

tinned  114 

Paints,  Non-corrosive  10 

Paladium    Hydrogen     absorbed 

by  229 

Palm  oil  used  with  beef  tallow 

gives  good  results 142 

Parson's  patent  for  Elec.-Galv.  148 
Patents    covering    Schoop    pro- 
cess        95 

Physics,  Laws  of,  as  applied  to 

Hot  Galv 18 

Pickle,  Hot  better  than  cold..  210 

Hydrofluoric  acid  212,  263 

Muriatic   acid,  A   "safe" 49 

Nitric  acid  211 

"Quick,"  Formula  for 50 

Sulphuric  acid,  Test  of 262 

Time   required   210 

Pickled   work,    Handling 48 

Pickling 44 

Acid,  Consumption  in  46 

Best  mechanical  method 46 

Black  46 

Cold  better  than  hot  50 

Foundry  49 

Fumes,  Effect  of  in  Sher....  278 

machine,  Automatic 45 

malleable  and  gray  iron  cast- 
ings    263 

Mechanical  44 

Over    45-47 

Over,  Remedy  for  135 

Securing  uniform  action  with 

acids   44 

Sheets  44-46,  111 

Solutions,  Length  of  time 
they  may  be  used  satis- 
factorily    50 

Solutions,  Temp,  of 262 

Steel  261 

Tanks 233 

Temperature  in  using  Hy- 
drofluoric acid  49 

Under  45 

White   .  46 

Wrought  iron  and  steel 48 


Pin  Holes  filled  by  Schoop  pro- 
cess    104 

Pipe   and   tube    Galv.   machine, 

Hanson  and  Van  Winkle..  189 
Cleaning   conduit   with    sand 

blast   213 

Water  Furnace  for  Sher 248 

Pipes,  Galvanized  11 

Pistol,   Distance    it    should    be 
held  from  work  in  spraying 

103 

for  metal  spraying,  construc- 
tion details  99 

for  metal    spraying,    Opera- 
tion of  101 

for  Schoop  Metal  Spray  Pro- 
cess      98 

Table  of  operating  costs  for 

one  hr.   105 

Pitch   lined   tanks   208 

Plans  for  Hot.  Galv.  plant..!5,  16 

Plans  of  Elec.-Galv.  plant 150 

of  small  galvanizing  kettle..     21 
showing  brickwork  of  galvan- 
izing kettle 22 

Plant,  Elec.-Galv 150 

and     equipment     for     Elec.- 
Galv 149 

and  equipment  for  Hot  Galv.  14 
and  equipment  for  tinning..  106 
and  equipment  for  tinning 

gray  iron  129 

Plate   Drying   17 

Plates 24 

Coping    25 

Platform   Cooling 247,   248 

Loading  , 246,  248 

Plating  and  cleaning  in  combin- 
ation    : 216 

Platinum,   Spongy,  Oxygen  ab- 
sorbed by  ~ 229 

Porous  condition  of  metals! 229 

Porter   machine    for    removing 

surplus  zinc  — ..     71 

Position  and  location  of  pickl*' 
ing  and  cleaning  tanks.......  2^3 

Potash  solution  for  Elec.-Galv.  196 
Potthoff's  Elec.-Galv.  barrel....  168 

Potthoff  Tube  Galv.  Machine..  191 
Powdered     metals,    Use    of    in 

metal  spraying  96 

Precipitation  of  Vapor,  How  it 

occurs  on  metal  229 

Preece  Test  290,  294 

Test,  Limitations  of 291 

Test,   Objections  to 297 

Test,  Operation  of 290,  294 

and   lead   acetate   tests   com- 
pared    301 

Preparing     cleaned    work     for 
dipping  in  hot  zinc 64 


322 


INDEX 


Preparing    gray    iron    castings 

for   tinning    133 

material  for  Sher 261 

work  for   Elec.Galv 209 

Prevention  of  corrosion 9 

Producer  gas,  Cost  of  in  Sher.  285 
Protecting       pyrometer       from 

action  of  molten  zinc 34 

Protection  of  iron  from  rust....       9 
Pumice  stone,  Use  of  in  clean- 
ing work   214 

Pure  water  test  for  Galv.  coat- 
ing    225 

Pyrogallol,  Its   effect  on   Elec.- 
Galv. bath 222 

Pyrometer   233,    255 

important     as      temperature 

regulator  35 

_in  proper  position  35 

of  advantage  on  sheets,  wire 

and  other  straight  work..     34 
Protecting   stem  from  action 

of   zinc   34 

Selecting  a  reliable   one   im- 
portant       37 

Stupakoff's  paper  on  35 

Use  of  in  Hot  Galv.  kettle..     34 

R 
Rack      for       re-tinning      small 

articles  124 

Re-charging  tumbling  barrel..     55 
Reducing  agents  for  Elec.-Galv. 

solutions  222 

Refinishing  old  galvanized  and 

tinned  work  146 

Regulation  of  zinc  deposit 223 

of  zinc  deposit  in  Elec.-Galv.  223 
Remelt       spelter       vs.      Prime 
western  Calorific  value  of     68 

Removing  oil  or  grease 210 

sand  from  casting 210 

Re-tinned   work,    Finishing 127 

Re-tinning  kettles,  Replacing..  128 

Method,  of  handling  work 125 

plant  and  equipment 121 

plant  containing  four  kettles, 

Elevation  of  122 

plant  with  four  kettles,  Plan 

of  123 

Rack  to  prevent  "nesting"  of 

small  articles  124 

stamped  ware  121 

Rheostat,  Adjustment  of 161 

Rolling  barrel  for  tinning  gray 

iron  castings  129 

improves   appearance    of    tin 

coating   112 

water,     Removing    scale     by 

51,  113,  136 
Wet  and  dry 51,  213 


Root   Wire    Cloth   Machine 202 

Rotation    of    drums    in     Sher. 

237,  267,  273 

Roughing   119 

Rust  preventative,  Zinc,  best..     11 
prevention,  Metallic  method       9 
prevention,  Non-metallic  me- 
thod         9 

Removing  16 

Removing  from  castings  with 
sulphuric  acid  Ill 


Saddlery,     hardware,     Tinning 

of  109 

Sal  ammoniac  42 

Action  of,  in  kettle 69 

Dip  for  a  flux  65 

Gray  granulated  forms  flux  42 
in  Elec.-Galv.  solution... .221,  222 
mixture  for  cleaning  castings 

in   tumbling  barrel 55 

Skimmings  84 

Skimmings,    Method    of    recov- 
ering       90 

Skimmings   often   shipped   in 

bulk  90 

Skimmings,  Storage  of 89 

Saline  or  salt  spray  test.... 225,  304 
Salts,     Epsom     in     Elec.-Galv. 

solution    220 

Spray  test  225,  304 

Spray     testing    box,    Details 

of  311 

Samples  for  testing.. ..288,  292,  309 
Sand,    Condition   of,    for    sand 

blasting  64 

Removing  from  castings 210 

Removing     from     gray     iron 

castings 133 

Removing     from     gray     iron 

castings   for  tinning 135 

Sand   blast  barrel,    Details    of 

construction    63 

barrel,  Operation  of  61 

Rolling  barrel 61 

Use     of     makes    tinning    of 

castings    simple    58 

valuable    in    cleaning    sandy 

gray   iron    castings 135 

Sand  Blasting 58,  135,  213,  261 

Air  pressures  required 60 

and  tumbling  51-65,  213 

Apparatus,  Operation  of 59 

Food  choppers,  Time  requir- 
ed for  59 

Machine,    Automatic     rotary 

type  61 

Machine,  Single  hose  type....     60 

Machine,   Two  hose  type 59 

Protection  of  Operator  in....     62 


INDEX 


323 


Sand  blasting 
quickly  cleans  "old"  work....     59 

Rev.   per   Min.   in  barrel 61 

Roof,   Construction   and  ven- 
tilation  of   62 

Saddlery  hardware  59 

Superior    on    light    and    deli- 
cate castings  61 

Use  of  grit  and  shot  instead 

of  sand 64 

Value  of,  in   Elec.-Galv.   and 

Sher 59 

Sawdust  in  zinc,  Effect  of 281 

Use  of  in  tumbling 213 

Scale,  Removal  of,  Time  requir- 
ed.for  47 

Removing  16 

Removing  by  sand  blast 

58-65,  213 
Removing  by  water  rolling  51 

113,  136 

Removing  from  wire 119 

Removing  with  muriatic  acid 

48,  113 
Removing      with       sulphuric 

acid  47,  111 

Schoop  Metal    Coating    Process 

Coating  with   aluminum   by     96 
Schoop  Metal  Spray  Process....     94 
Detail  of  old  stationary  type     96 
Details  of  first  portable  appa- 
ratus       97 

Details   of  pistol   99 

Evolution  of  apparatus  used     95 
Method   of  holding  "pistol"  103 

of  applying  the  coating 101 

Operation    of    first    portable 

type  of  apparatus 96 

Operation  of    old    stationary 

type  95 

Operation  of  the  cyclone  ap- 
paratus       98 

Pistol,  Gas  pressure  required  101 

Pistol  type  of  apparatus 98 

will  fill  pinholes  and  defects 

in  sheets  or  coatings 104 

Schulte's  Elec.-Galv.  barrel 172 

Grinding  and    scouring    ma- 
chine   : 213 

Wire  Galv.  machine  204 

Scoop,  Dross,  Construction  of..     33 
Scouring  and  grinding  machine  213 

Scratch  brushing  211 

Screener  dust 276 

Screening  machine,  Dust..233,  251 
Screw        conveyer        machine, 

Daniel's  158 

Screws,   Allowance    for    thick- 
ness of  coating  in  Sher....  268 
Equipment  for  Sher..; 233 


"Scruff"  or  dross,    Method    of 
handling   work   to   prevent 

the  attachment  of 125 

Setting  small  galvanizing  kettle 

without  ash  pit 20 

Sheet     steel,     Temp,     for     Hot 

Galv.  of 68 

Sheets,  Bright  Galv 74 

Determining  spelter  coating  310 
Formula   for   Elec.-Galv.   of  218 
Hot   Galv.,  by    Bayliss    pro- 
cess        76 

Hot  Galv.,  by  hand 73 

Hot    Galv.,    Construction    of 

machine  for  74 

Hot  Galv.  of  73 

Material      required     to    Hot 

Galv 75 

Pickling  44,  46,  111 

Schulte     machine      for      Elec. 

Galv 204 

Sher.  test  of  296 

Tests   of  durability 225 

Sherard  Cowper-Cowles,  Inven- 
tor of  dry  Galv.  process....  227 
Sherardized  steel  magnified  100 

times  228 

Steel  magnified  1300  times..  229 
Sherardizing     articles       which 
cannot  be  successfully  coat- 
ed    231 

Art  of   227 

Cause  of  black  spots  in 279 

Cause  of  unsatisfactory 232 

Cleaning  most  important  op- 
eration in  232 

Cleaning  very  essential 280 

Coloring  and  finishing 282 

Cost  per  ton 284 

Cutting     down    'screws    and 

threads  267 

Definition  of  228 

Depositing  copper  or  bronze 

after  282 

Discovery  of  227 

Dont's  in  practice  278 

Drums  233 

Drums,    Life    of 250 

Fats  will  redeposit  in 281 

Flaked  work  cause  of 281 

Furnace   233 

Furnaces,  Coke  burning..234-240 
Furnaces, Controlling  heat  of  238 
Furnaces.Electrically  heated  248 
Furnaces    Elec.    heated,    Op- 
eration of  271 

Furnaces,  Elec.  heated,  Pack- 
ing    266 

Furnaces,  Gas  and  oil  burn- 
ing     ....229-248 

General  operation   275 


324 


INDEX 


Sherardizing 

Heavy  deposit  275 

in  prehistoric  times 227 

Inspection  of  material  before  279 

Japanning  after  282 

Lacquering  over  283 

Materials   used   in 256 

Motion  during  273 

Must   not   be   done    in    same 

room  as  pickling 278 

Nickling  over  282 

Non-uniformity      of     coating 

remedied  279 

Not    a   solder    281 

or  dry   Galv 227-286 

Plant,    Floor    space    required 
for   daily    capacity   of   one 

ton  233 

Plant,    Location    and    equip- 
ment of  233 

Plant,  Typical  floor  plan  233,  234 

Preece  test  for 294 

Preparing  material   for 261 

Pure  zinc  gives  best  results  231 

Temp,  and  deposit  chart 270 

Temp,  in  256,  257,  262,  267, 

270,  275,  279 

Temp.  Uneven  effect  of 279 

Test,  Salt  spray 225,  304,  311 

Testing  by  electrolytic  meth- 
ods    302 

Theory  of   228 

Time  required  for..257,  272,  275 

Value  of  zinc  oxide  in 231 

Various   stages   of 231 

with  Zinc  under  vacuum 272 

Shot  used  instead  of    sand    in 

sand   blasting 64 

Sinks,       Temp,     suitable       for 
Galv .'. 68 

Size  of  conductors,  Figuring..  207 

Skimmer,  Use  of 89 

Skimmers  32 

Skimming  kettle   for   removing 
surplus  tin  in  re-tinning..  127 

Skimmings,   Dry  zinc 84 

Sal  ammoniac  84 

Sal    ammoniac,   Recovering..     90 
Sal   ammoniac,   Storage   of..     89 
Slabs   of  spelter,   Arrangement 

of  in  kettle  67 

Slag  burnt  in,  Effect  on  Sher..279 
Slag,  Removal  of  from  tinning 

kettle    141 

Smooth   coatings   .Agents  which 

produce  222 

secured      by      using-      grape 

.sugar  218 

"Soaking"  kettle   ...  ...  121 

Soda,  Caustic,  Test 293,  303 


Sodium  acetate    in    Elec.-Galv. 

solution    221 

Aluminum,  Chloride  in  Elec.- 
Galv.   solution  221 

Citrate    in    Elec.-Galv.    solu- 
tion      221 

Sulphate     of     in     Elec.-Galv. 

solution 218,  219,  220,  222 

Solution,   Caustic   soda 210 

for  testing    Elec.-    and    Hot 

Galv 287 

Lime  to  neutralize  acid 262 

Solutions   for   Elec.-Galv 217-222 

for  Elec.-Galv.  in  open  tanks  218 

Pickling,   Temp,   of 262 

Spangled,  Preparing  work  to  be  68 
Spraying     pistol,      Details     of 

construction 99 

Specifications,   Galv 287 

Spelter,  Coating  of  sheets,  De- 
termining    310 

Coating  of  wire,Determining  310 
Packing  slabs  in  new  kettle  66 
Prime  Western,  vs.  Remelt, 

Calorific   value   68 

Selecting  best    for    the    pur- 
pose        42 

Slab   zinc   41 

Spirella  Co's   Elec.-Galv.  plant  150 

Spongy  deposits,   Cause  of 223 

Spoons,  Iron,  Tinning  of 109 

Steel   Tinning  of   119 

Stamped  steel.Wet  tumbling  of  213 

ware,  Retinning  of  121 

Steel,     Elasticity     changed    by 

temp,   and  length  of  dip..     80 
and    wrought     iron,     soluble 

value  of  18 

Hot   and    cold    rolled    clean- 
ing of  209 

Pickling  48,  261 

Pipe,    Temp,    for    Hot    Galvt 

of  * 68 

Proper  grade  for  making  Hot 

Galv.  kettles   18 

Sher.  magnified  228,  229 

Stamped,  Wet  tumbling  of..  213 

Tinning  of  106 

Sticking     together     of     work, 

How  prevented  71 

Storage  tanks  48,     57 

Storing  castings  after  tumbling  57 
Strength  of  wire  influenced  by 

Hot  Galv '    78 

Strike  zinc  223 

Stringing  work  for  Hot  Galv.     70 
Stupakoff,   S.H.,   Paper   on   py- 
rometers       35 

Sublimation  228 

Sugar     grape     in     Elec.-Galv. 
bath   218,   221 


INDEX 


325 


Sulphate    Iron    in    Elec.-Galv. 

bath  221 

of    aluminum    in    Elec.  Galv. 

solution 218,  220,  221,  222 

of  copper  test  226 

of  sodium   in   Elec.-Galv.   so- 
lution    218,   219,   220,   222 

of   Zinc   Elec.-Galv.   solutions 

218,  219,  220,  221,  222 

Sulphuric  acid  43 

Cleaning  sandy  castings..49,  112 
for  cleaning  sandy  gray  iron 

castings  135 

in  Elec.-Galv.  solution 

219,  220,  221 

pickle  49,  211 

Pickle,    Test   of „ 262 

Removing  scale  with Ill 

Substitutes  for  48 

Tanks  for  16 

Test  for  Galv.  coating 22 

Use   in   cleaning  sandy  cast- 
ings       49 

Use  of  in  removing  scale 47 

Surplus  Tin,  Method  of  remov- 
ing    118 

Removal    of    in    "skimming" 

kettle  127 

Removing   from   wire   tinned 

in  coils  119 

Surplus  Zinc,  Removal    by    me- 
chanical means  71 

Removal  of  from  wire  cloth     77 
Removing    from    castings    by 

brushing    70 

Removing     from    work    dip- 
ped  in   baskets 71 

"Sweating"  prevented  in    plat- 
ing by   tinning  first 129 

Sweating  zinc  dross  87 

Sweepings   from    Sher.   plant..  281 

Switchboard  149 

Switching     box,      Construction 
and  use  of 143 


Tallow    in      re-tinning     kettle, 

Condition   of  - 123 

Tank  for  kerosene  118 

Tanks,  coating  by  Schoop  pro- 
cess   104 

for  acid  and  water 30 

for  caustic  soda 114 

for  cleaning    sandy    castings 

with   Hydrofluoric    acid....  134 
for     copper    bath     in     Elec.- 
Galv 198 

for  elec.  cleaner  149,  215 

for    Elec.-Galv.    Construction 

of    208 

for  tinning  107 


(Tanks,  Hydrofluoric   16 

Lining  with  sheet  leads        .     31 

Pickling  208,  233 

Pickling  and  cleaning,  Loca- 
tion    233 

Oil,   Construction  of 142 

Rinsing  114 

Sulphuric  acid  16 

Washing  165 

Water 16,     108 

Wooden,  Construction  of 31 

Tannic  acid,  Its  effect  on  Elec.- 
Galv.  bath  222 

Tartaric     acid     in    Elec.-Galv. 

solution 221 

Tea  kettles  cleaned  in  tumbling 

barrel 54 

Temperature  caustic   Soda  test 

293,  303 

in  Hot  Galv 20,  36,  67,  68 

in  Preece  test 290,  294,  297 

in  Sherardizing  256,  257,  262, 

267,  270,  275,  279 

in  Sher.  chart 270,  271 

in  tinning 115,  117,  118 

of  hydrofluoric  acid  pickle..     49 
of  molten  zinc,  Effect  of  at- 
mospheric conditions  on....     39 

of  tin  for  coating  on 39 

of  tin  for  coating  gray  iron 

castings  117,  141,  142,  144 

Methods  of  calculating  num- 
ber of  degrees  drop  per  hr. 
in  molten  zinc  while  cool- 
ing    38 

Natural  actions  in  tank  en- 
abling experts  to  accurate- 
ly judge  37 

of  zinc  required  to  secure  un- 
iform coatings  by  hot  pro- 
cess    35 

Regulating  by  pyrometer 34 

Too      much      heat      destroys 

kettle  37 

Variation  affect  tests 297 

Temperatures     determined     by 

color  of  zinc,  etc 68 

Test,  Caustic  soda 293,  303 

Cinder  for  Galv.  coating 225 

Copper  sulphate    or    Preece, 

290,  294,  301 

for  neutral   Elec.-Galv  bath  223 
for  thickness  of  zinc  coating 
on  armored  cable    strip....  226 

Government  303 

Hydrochloric  acid  and  anti- 
mony    308 

Lead  acetate  291,  299 

Lead  acetate,  Advantages  of  301 

Moist   air 226 

of  hydrofluoric  acid  pickle....  263 


326 


INDEX 


Test,  Preece 290,  294,  301 

Pure    water    for    Galv.    coat- 
ing    225 

Salt  spray  225,  304 

Sulphate  cf  copper 226 

Sulphuric  acid  for  Galv.  coat- 
ing    225 

Zinc  coating  226,  287,  312 

Testing  box,    Salt   spray 809 

Salt  spray,  Details  of 311 

Material     for    mfr.     of    Hot 

Galv.  kettles   19 

Zinc   dust  for    metallic    con- 
tent      258 

Tests,    Galvanizing    283 

Comparative  225,  304-307 

Percentage  of    error    due    to 

temp,  variations 297 

Preece      and      lead     acetate 

compared  301 

Used   to    determine    strength 

of  wire  79 

Theory  of  Corrosion  11 

Thermometer,  Method  of  using     39 

Time  required  for  testing 292 

required  for  Sher...257,  272,  275 

required  for  tumbling 55-57 

required  in   Hot.   Galv 69 

required   in    Elec.-Galv.     218, 

219,  223 
required  to  clean  sandy  gray 

iron  castings 135 

Tin,  "Boiling"  to  prevent  dross 

from  interfering  with  workl£7 
Coating  applied  in  a  molten 

spray  94 

Dipping    gray    iron    castings 

in  138 

not  electro  positive  1 

Proper  temp,  of 117 

Surplus,    Method    of    remov- 
ing    118 

Surplus,  Eemoval  of  in  "skin- 
ning" kettle  127 

Surplus,  Removing  from  wire 

tinned  in  coils  119 

Temp,  of  106,  115,  118 

Tinned  work,  Old  refinishing..  146 

Tinning,  Applying  the  coating  115 

castings    with    three    kettles 

of  tin  144 

Fuel  for  107 

gray  iron,   Plant  and    equip- 
ment for  129 

gray  iron  castings 129,  138 

gray  iron  castings,  Flux  for  138 
Gray  iron  castings    must    be 

absolutely  clean  for 136 

gray    iron    castings,    Prepar- 
ing work  for 133 


Tinning,     gray     iron    castings, 

Proper  heat  for.... 138,  141,  144 
gray  iron  castings,  Time  re- 
quired    138,   141 

iron   spoons   109 

•  kettle,   Flux  for 139 

kettles,  Materials  used  in  con- 
structing    144 

malleable  iron  castings 106 

Passing  work  through  kettle  117 
Plant     and    equipment    106, 

130,  144 

Plant,  Drainage  of 109,  130 

Plant  for  gray  iron  castings  130 

Preparing  work  for  Ill 

Steel   106 

Steel  spoons  119 

Time  to  prepare  castings  for     59 

Tools  and  kettles  for 109,  116 

Wire   in   coils   : 119 

with  two  kettles 116 

Wrought  iron  106 

Tongs  31 

for    re-tinning,    Construction 

of  127 

Proper  use  of  70 

Self-acting,  on  Hot  Galv.  ma- 
chine    75 

Use  of  in  Hot  Galv.  sheets....     73 

for  Hot  Galv 31 

for  tinning  109-116,  119,  142,  143 
Tragacanth,     Gum,     in     Elec.- 
Galv 221 

Its  effect  on  Elec.-Galv.  bath  222 
Transfer  car,  Construction  of  253 

Trucks,  Transfer  233 

Tube  and  Pipe  Galv.   Machine, 
Hanson  and  Van  Winkle..  189 

Galv.  Machine,  Potthoff 191 

Tubes,  Automatic  Galv.  of 81 

Comparison  of  cost  of  Galv. 

by  hand  vs.  machine 83 

Handling  of  to  prevent  trap- 
ping of  air  while  Elec.- 
Galv 194 

Hot  Galv.  of 77 

Machine  for  Hot  Galv 82 

Tubing  Furnace  for  Sher 248 

Tumbling  51,  113,   136,  213 

and  sand  blasting 149,  213 

Tumbling  Barrel,  Charging 213 

Construction   of 53 

Leaving  work  in  it  over  night  56 

Loading  of    54 

New  cleaning  preparatory  to 

using  57 

Operation  of  54,  136 

Recharging    of 55 

Rev.  per  Min 61 

Solution  for  cleaning  casf- 
ings 55,  57 


INDEX 


327 


Tumbling  Barrel 

Speed  for   cleaning    castings 

55,  57,  60 
Time  required  to  clean  work 

in  55 

Tumbling  Dry 52,  209,  213,  283 

Dry,  of  wire  work 213 

Gray  iron   castings 133 

Time  required  for 55,  57 

U 

Under  pickling  45 

Unloading  and  cooling  drums  276 

Elec.-Galv.  barrel 168,  173 

Unskilled  labor  in  Hot  Galv...     13 


Vacuum,  Sher.  with  zinc  under  272  i 
Vapor,   Effect  of  free    ions    on 

precipitation   230 

Precipitation  of 229 

Tension  230,  231,  270 

Zinc,  Methods  of  producing..  230 

Vegetable  cutters,  Tinning  of  129 

Ventilation  of  Hot  Galv.  plant  14 

of  sand  blasting  room 62 

Voltage   193,  223 

differences   153 

for    Elec.    Cleaner 216 

for   Elec.-Galv 218 

Proportioning  of  ..              ...  207 

W 

Washer  foundation,  Cast  iron     25 

Washing  tank  165 

Water      heater,       Coating     by 

Schoop  process 104 

Rolling  51,  61,  113,  136 

Rolling   gives   better   finish..     58 

Tanks,  Construction  of 30 

tanks    for   tinning   plant 108 

Watrous  machine  72 

Wet  rolling  barrel  gives  better 

appearance  to  work 58 

Whipping  box  for  tinning 108 

White  pickling   46 

Winter,    Dr.    Heinrich,    Paper 

on  strength  of  wire 78 

Wire      Cloth     Elec.-Galv.     Ma- 
chine   King's 194 

Formula   for   Elec.-Galv.   of  218 

Machine  for  Hot  Galv 77 

Machine,   Root's   202 

Hot  Galv.  of 77 

Influence  of  Galv.on  strength  78 
Wire  Netting,  Elec.-Galv  of....  194 

Hot  Galv.  of 77 

Wire,  Schulte  machine  for  Elec. 

Galv 204 

Sher.  test  of 296 

Test  308,  310 

Testing  samples  288 


Wire,  Tinning  in  coils 119 

work,  Dry  tumbling  of 213 

Wiring      diagram,      for      Elec. 
heated  Sher.  furnace..249,  250 

Wrought  iron  pickling 48 

pipe,    Temperature    for    Hot 

Galv 68 

Tinning  of  106 


Zinc,  ammonium  chloride  better 

than  sal   ammoniac 42 

Zinc  ashes  84 

Method  of  recovering 90 

Recovery  of  fine    not    profit- 
able       91 

Screening  of  a  good  practice     91 

Storage  of  90,  91 

Zinc  best  rust  preventive 11 

Boiling  point  of 272 

Chloride   in   Elec.-Galv.   solu- 
tion   218,  219,  220,  221 

Zinc  coating  applied  in  a  molten 

spray  94 

by   Elec.-Galv.   process 148 

Cost  of  by  Schoop  process....  102 
Schoop  metal  spraying  pistol     90 

Spec,  for 287 

Table  of  tests  on  Elec.-Galv.  304 

Thickness  of  267 

Thickness  of  in   Schoop  pro- 
cess      102 

Zinc   colors    indicate    tempera- 
tures       68 

Corrosion  saves  the  iron 12 

Deposit  on  sheets  by  Health- 
field  process   76 

Zinc   dross  256 

cooling  in  kettle  bursts  it....     86 

Hard  84 

Kettle  for  recovering 87 

Method  of  recovery 85 

sweating  or  running  over....     88 

sweating  87 

Zinc  dust  256 

Analysis  of  274 

Color  no  proof  of  coating....  281 
Cost  per  ton    of    Sher.    ma- 
terial    284 

Drying  out  257 

Fire  in,  How  to  put  out 281 

Freeing  it  from  iron 257 

Metallic  content  267 

Determining  metallic  zinc....  258 

Oxidation  of  274 

Oxidizes     when     sawdust    or 

excelsior  is  mixed  in 281 

Properties    of    274 

Receptacle  for  233 

Saving   of    281 

Storage  of 266 


328 


INDEX 


Zinc   Dust,   Used,   Disposal 285 

Zinc  electro  positive  to  iron....     11 

Iron    alloy    227 

Melting  point   35 

Melting  point,  Schoop  process  99 

Overheating,  Loss  from 67 

Oxide  Value  of  in  Sher 231 

Oxidizing  prevented  to  flux     69 
Pure,   gives    best     Sher,    re- 
sults        231 

Residue,  Disposal  of 285 

Skimmings,  Dry 84 

Slab  or  spelter 41 


Strike  223 

Sulphate  in  Elec.-Galv.  solu- 
tion   218,  219,  220,  221,  222 

Zinc  Surplus,  Removal  of 70-71 

Removal   of  by    Porter    ma- 
chine       71 

Removal  by  Watrous  machine  72 
Removal  of  from  wire  cloth     77 

Zinc,  Temp,  of 67 

Under  vacuum,  Sher.  with....  272 
Vapor,    Methods    of    produc- 
ing    230 


TS 

660 

F6lg 


Flanders  -  Galvanizing  and  tinning 

UNIVERSITY  OF  CALIFORNIA  LIBRARY 

Los  Angeles 
This  book  is  DUE  on  the  last  date  stamped  below. 


1956 


Form  L9-100m-9,'52(A3105)444 


' 


Bogineerina 
Ubnrg 


niUMin 

A     000768169     5 


0.  Ir»koff 


SEP      73 


&• 


